Sciencemadness Discussion Board - Acetaldehyde synthesis

Acetaldehyde synthesis

plasma - 3-6-2002 at 02:24

Does anybody have a synthesis for this, besides megalomanias. (I don't have sodium dichromate)

vulture - 3-6-2002 at 08:56

Maybe oxidation of ethanol with hydrogenperoxide? While I think of it, this must require a catalyst.

Nick - 3-6-2002 at 09:30

C2H5OH + H2O2 does work, if you add a catalyst. I used a few grains of K2Cr2O7, but a little KMnO4 would work.
Trouble is, yields are low, and if you use conc. reagents then runaway can occur.
Another way is passing air and ethanol vapour over hot copper, then distil the ethanal from the ethanol and ethanoic acid.
Maybe you could reduce ethanoic acid with Na2S, or mix it with HCl and slowly add zinc dust (not quite enough to react with all the HCl), then distil off the ethanal.

plasma - 4-6-2002 at 11:23

Will this work :

HCHO + CH3OH -> CH3CHO + H2O

Thanks !

madscientist - 4-6-2002 at 11:39

Sorry plasma, that won't work; organic chemistry isn't as straightforward as inorganic. :-/

Nick, are you sure that using KMnO4 will work as a catalyst in a H2O2 / CH3CH2OH reaction that is to form CH3CHO? KMnO4 oxidizes H2O2 readily, causing both to decompose... I have tried adding two or three grains of KMnO4 to a test tube 1/4 of the way filled with 27.5% H2O2, and the result was a violent, hot, oxygen gas / steam forming reaction. All that was left was some very hot water, and Mn3O4 (I believe that's what the dark brown precipitate was).

madscientist - 4-6-2002 at 12:00

I have more to say:

CH3CHO can also be prepared by the dehydrogenation of CH3CH2OH. I think there is some discussion on this method of preparing CH3CHO somewhere on this board. This is the reaction that occurs when hot ethanol vapors are passed over hot copper metal in the absence of oxygen:

CH3CH2OH --(Cu)--> CH3CHO + H2

I'm certain that ethanoic acid and sodium sulfide will react to form merely hydrogen sulfide and sodium acetate.

Is this how the proposed CH3COOH / HCl / Zn process is supposed to work?

CH3COOH + 2HCl + Zn --> CH3CHO + H2O + ZnCl2

If so, I'm almost completely certain that it won't work. :-/

Edited to add: http://www.sciencemadness.org/talk/viewthread.php?tid=9
There is some discussion on preparing CH3CHO via dehydrogenation of CH3CH2OH in that thread.

[Edited on 4-6-2002 by madscientist]

Nick - 4-6-2002 at 12:40

Yes, I am certain that KMnO4 will work. Only use a TINY amount, or the H2O2 will be decomposed too fast. Copper turnings may be better, basically anything that decomposes the H2O2 will work.
I'm not surprised you got a hot, violent reaction when adding KMnO4 to 28% H2O2! Like I said, conc. reagents = runaway. I used 9% H2O2 and vodka, and it was nice and gentle but not very high yielding.
Ethanol and hot copper works without oxygen, too? That's interesting.
(D'oh! Yes, sulphide + acid --> salt + H2S, I forgot...)
I haven't seen HCl + Zn used to reduce carboxylic groups before, but I know it works on nitro groups. It might be worth trying. Basically, the HCl and Zn react to produce atomic hydrogen, which reduces the thing you're trying to reduce. You need quite a large excess of HCl and Zn, because the atomic hydrogen will quickly react to form molecular hydrogen if it isn't oxidised soon enough.

Dichromates

Polverone - 4-6-2002 at 20:02

It is possible, though perhaps not convenient, to prepare dichromates from more readily available precursor materials. K2CO3 + 2KNO3 + Cr2O3 + lots of heat = 2K2CrO4 + 2 NO + CO2. I tried this today and it works fairly well, but be warned that fairly intense heat is needed (a good propane flame), and you may also need some extra carbonate/nitrate if they decompose before acting on the Cr2O3. I believe that this should work when substituting the corresponding sodium salts also. The addition of enough sulfuric or nitric acid to turn the mixture somewhat acid (around pH 4?) will convert a chromate solution to dichromate. There is an obvious color change. In most applications, one wishes to separate the nitrate/sulfate that is also formed in this process. But for oxidizing ethanol, I don't think potassium nitrate/sulfate would much interfere, since you're going to distill anyhow. K2CO3 and Cr2O3 are available cheaply as ceramic materials. NaNO3/KNO3 sources are obvious. Na2CO3 is readily obtained for many purposes or made by heating baking soda.

vulture - 13-6-2002 at 10:26

How about strongly heating copper wool until it gets black (CuO) and than quickly dumping it into ethanol?

Rhadon - 13-6-2002 at 12:51

CuO and C2H5OH does work, but if you just use copper wool you'll get problems if you want to make larger amounts of acetaldehyde.
It would be a better idea to use pure CuO which can be made by electrolysis of Cu.

vulture - 14-6-2002 at 07:50

Doesn't the CuO need to be hot in order to split it's oxygen?

Rhadon - 14-6-2002 at 12:26

Hmm, I think you're right. Anyone knows how hot the CuO will have to be?

T. Bond - 2-8-2002 at 08:35

Vulture and Rhadon, there is another way to skin the CuO.

Copper Oxide can be reduced with H2(g) yeilding Cu(s).

CuO + H2(g) ==> Cu(s) + H2O

I am wondering if its possible to reduce acetaldehyde back to ethanol other than thru NADH reaction? Any suggestions?

vulture - 8-8-2002 at 10:58

Err, Mr. Bond, if I may call you that way, the problem was not making copper!

plasma - 20-9-2002 at 23:07

I have pure CuO. I think I'll just heat some of it and drop in the right amount of C2H5OH. Does any body know the required temp ?

a_bab - 21-9-2002 at 01:31

For this reaction the CuO should to be red hot. It can be heated in a tube than passing the alcohol vapors thru the tube. BUT it'll work only with methanol; I tryed once both and it didn't worked with ethanol. With methanol works perfectly.

It's enough to heat a copper wire (whool) in order to oxydise it and if you put it quickly in a test tube containing methanol; the vapors will quickly decompose the copper oxide leaving the wire in a nice red color of pure copper.

Dudes..........come on now, do you all love the hard ways or what?

PrimoPyro - 21-9-2002 at 04:06

The simplest way to make acetaldehyde with little byproducts is simple treatment of ethylene glycol (common radiator antifreeze in the USA) with dilute aqueous H2SO4. This is called the Pinacol Rearrangement.

Pinacols are vicinal glycols, meaning 1,2-diols of course.

HO-CH2-CH2-OH + H+ ---> HO-CH2-CH2-OH2+ ---> HO-CH2-C+H2 ---> -O-C+H-CH3 ---> CH3-C(H)=O.

Basically, one alcohol gets protonated, then the dehydrating abilities of H2SO4 remove water, forming a carbocation, which rearranges to the more stable carbocation, which is the one on the carbon with the other hydroxyl, and then the alcohol extrudes a proton (so the protonic acid is a catalyst, not a reactant) and the O-C bond strengthens to a double bond.

The Pinacol Rearrangement is used all the time in clandestine labs, for rearranging 1-phenyl-propan-1,2-diols to 1-phenyl-2-propanones, which are direct precursors for amphetamines and methamphetamines.

The Pinacol rearrangement also works on epoxides because the acid opens the epoxide ring to the diol with the water present.

All that need be done is heat some ethylene glycol and dilute H2SO4 together for awhile. There are nearly zero side reactions. Zero that I know of, but Im covering my ass just in case. :p

Come now, this is so much cheaper than using all these inorganic reagents.

PrimoPyro

Carbocations?

vulture - 22-9-2002 at 03:41

Are you sure there are carbocations intermediates? I thought these only could be created by superacids? Or maybe this is a nomenclature problem again......

Organic VS. Inorganic

PrimoPyro - 22-9-2002 at 04:24

I have noticed that organic chemistry has slightly different definitions of certain things than inorganic chemistry, and this can cause problems during communication, possibly this is an example.

Yes, I mean carbocations, as in C+ species. And no, not just superacids create them. In fact, nearly any chemical can create a carbocationic intermediate. It is the responsible intermediate for nucleophillic substitutions, several eliminations, and many other concepts as well.

An insanely huge list of reactions and reagents are used every second to form carbocations in reality, for an equally insanely large list of reasons.

I would say that the carbocation intermediate is directly responsible for MORE than 50% of all organic reactions, in one way or another. There really is no method for me to convey just how often they are encountered in organic synthesis.

The intermediates are not isolatable. They exist for perhaps only microseconds, before they react in the desired reaction to form the product or yet another intermediate.

As for what you thought I was saying, I do not know. If you explain what you don't understand or agree with, perhaps I can comment further.

PrimoPyro

figured it out....

vulture - 22-9-2002 at 06:17

... I "misphrased" over there, I think superacids are the only species to isolate carbocations in stable complexes, no?

acetaldehyde synthesis

BLAST_X - 3-10-2002 at 04:17

Have somebody try out this method,
to form acetaldehyde in 3 steps:

1. synthesis of acetylene (C2H2)
2. synthesis of vinyl alcohol [C2H4O]
3. decomposition to acetaldehyde

a example:
In a first flask with addition funnel drop
slowly H2O to calcium carbide (CaC2).
The forming C2H2 gas letting-in a second flask in a catalyst-mixture of H2SO4/HgSO4 which should coolled below > 15 C.
The forming ethanal can be separated from the mixture by distilling with a water-bad at >21 C, perhaps under vacuum.

Acetaldehyde can be used for instance to
synthesize pentaerythritol tetranitrate, when mixed with paraformaldehyde and then nitrated directly.

Acetaldehyde from Ethylene Glycol

Alchemist - 20-10-2002 at 16:28

Hello all,

I read somewhere that Acetaldehyde can be made from Ethylene Glycol and Sulfuric Acid (I think it was on the HIVE)! I tried it this week end and all I get is Dioxane (Diethylene Ether)! Has any one elese ever heard of getting Acetaldehyde rather than Dioxane? If you what have I done wrong! I believe the reaction is the called Pinacol rearrangement. I have read some on it, but have found no clues that Ethylene Glycol can be converted to Acetaldehyde.

Synthesis

TripleDamn - 22-10-2002 at 02:08

I believe you would talking about synthesis of 1,2-TPEGDN ?

vulture - 7-11-2002 at 06:09

If you're really in for a challenge, you can try reacting acetylene and water in the presence of a Hg salt.

2C₂H₂ + 2H₂O -> 2CH₃CHO

Why is subscript so f***** up?

ethylene glycol is nonsense

Organikum - 12-12-2002 at 10:17

this is from the MERCK index:

Title: Dioxane .
CAS Registry number: 123-91-1
Additional name(s): 1,4-Diethylene dioxide
Molecular formula: C4H8O2
Molecular weight: 88.11
Percent Composition: C 54.53%, H 9.15%, O 36.32%
Literature references: Prepd by distilling ethylene glycol with dil H2SO4 .
......

Thanks Alchemist I would have believed the nonsense. Ok a dioxane snthesis isn´t as bad.

ORG

/re: synthesis of Acetadehyde

solo - 12-12-2002 at 13:09

primo pyro.........some references for your claim, on the use of regular antifreeze and H2SO4 to make acetaldehyde I checked rhodium and althoudh I found th said reaction (Pinacol Rearrangement.) , I guess I just didn't see it clearly or specificallyfor (ethylene glycol) as you stated on your post. Since I have to make everything this is of some interest.

Noted also something about Zinc , HCl reducing the carboxylic acid to an aldehyde , something said by someone else , not you , but do you know or have you heard of such a procedure , I myself have been looking both in March's and literature about such reactions but have had no sucess.

thanks, Saludos , from Latin America

10fingers - 13-12-2002 at 16:32

Making acetaldehyde from ethylene glycol sounds interesting. I tried a little experimenting with it though and got nothing. I tried various concentrations of H2SO4 and different temps and it did not seem to react in any way at all.

madscientist - 13-12-2002 at 17:12

I recently attempted to dehydrogenate ethanol to yield acetaldehyde. I boiled 100mL of ethanol (denatured alcohol) and passed the vapors through a copper tube that was being heated by a propane burner. Initially, I wasn't cooling the condensation tube effectively enough, so only a small amount of non-dehydrogenated ethanol was being condensed, and resulting in my backyard being pumped full of a plasticy-smelling vapor, which I assume was acetaldehyde. I did manage to quickly get it cold. I ended up with around 60mL of liquid. I didn't have the chance to try to analyze it - I hopefully will do so soon.

10fingers - 14-12-2002 at 08:20

I tried the catalytic dehydrogenation of ethanal awhile back. I got a little bit of acetaldehyde but I was using a huge amount of ethanol. You also need to add air or oxygen to the ethanol before the catalyst. I think part of the problem with my system was that it did not have an efficient condenser for the acetaldehyde vapors. Acetaldehyde boils at 21* C so you really need to cool it down or most of it will be lost.
I saw a patent where they ran the vapors into cold water to capture the acetaldehyde. I assume that then you have to distill the acetaldehyde out of the water.

Marvin - 17-12-2002 at 03:44

I dont think you should be adding oxygen before, maybe you are confusing catalyctic dehydrogenation with catalyctic oxidation. Youd distil acetaldehyde hydrate out of the water, which has a much higher boiling point.

Dehydrogenation, loss of H2, depends critically on the temperature of the catalyst for good yeilds, if you get a lot of undecomposed ethanol its probably far too cool.

solo - 17-12-2002 at 13:27

Note : here is a recent posting on the subject at the Hive,.......".Novel Discussions"

slothrop
(Newbee)
12-17-02 10:58
No 390260
Benzyl alcohols to Benzaldehydes

From Synlett 2002, 12, pp2041-42,
A Novel and Efficient Oxidation of Benzyl Alcohols to Benzaldehydes with DMSO Catalyzed by Acids
Typical procedure: A mixture of 557 mg of benzyl alcohol, 0.15 mL of HBr (48 %) and 5 mL of DMSO was stirred in an oil bath at 100°C. TLC (petroleum ether/diethyl ether, 1:1) was used to indicate the completion of the reaction (3 h). To the reaction mixture were added 5 mL brine followed by extraction with 30 mL of diethyl ether. The ether layer was washed with brine (5 mL x 4). Evaporation of the ether and subsequent buld to buld distillation produced 530 mg of benzaldehyde in 95 % yield.
//Tyrone Slothrop

ACETALdehyde

Organikum - 17-12-2002 at 17:00

hey, SOLO it´s acetaldehyde not benzaldehyde and I can by no way discover how to adapt this procedure for acetaldehyde.
So this will be grounded in my stupidity please tell me what I overlook.

Madscientist, am I right if I guess that Cu oxide is the catalyst in the furnace-tube reaction? Or what?
Pleaze all tell the whole story not missing the unimportant important details like whats the catalyst is. Yes?

thanks
ORG

madscientist - 17-12-2002 at 20:25

That procedure for preparing benzaldehyde from benzyl alcohol is actually of use. If an equamolar quantity of ethanol was substituted for benzyl alcohol, I suppose that procedure could be used to prepare acetaldehyde.

It's copper metal, not copper oxide, to my knowledge.

Don´t think so but I am not sure

Organikum - 19-12-2002 at 09:30

I don´t believe that it works for EtOH -> acetaldehyde, not at least because the author doesn´t claim thus (and what chemist wouldn´t if there was a chance it could?).
I remember also having read that not but....
I will try to look it up and find out whats up, also I won´t waste HBr on something what is doable with a plain coppertube.

Anyway, I have found this nice PowerPoint presentation: "Oxidative Preparation of Aldehydes and Ketones" It´s a good one IMHO:

[Edited on 19-12-2002 by Organikum]

Attachment: acetaldehyde.ppt (348kB)
This file has been downloaded 1234 times

RE: aldehydes

solo - 19-12-2002 at 10:47

Organikum: I just assume it would work, no proof just a feeling after seeing how it works on benzaldehydes. I liked the prsentation al aldehydes and ketones, I learned something.

I will be asking you about some details about the biotransformation .......as I set up my unit

Greetings, from Latin America

tube furnace

blazter - 19-12-2002 at 12:35

I have experimented a bit with a tube furnace to hopefully use it to produce acetaldhyde and formaldhyde. While i did not actually get it to work i did find that when i just had a stream of ethanol vapors from my boiler into open air i could put a pre-heated coil of #14 copper wire into the stream and it had a "shimmering" appearence. Also, while the heated coil was in the stream the vapors were no longer visible in the air as they were before. I assume that the reason the vapors were no longer visible was that they were converted so a vapor with a MUCH lower boiling point and therefore volitalized fully in the air. The tube furnace i have never worked because there was no way for me to admit a stream of air into the system to mix with the ethanol vapors. Sometimes i fould that when just starting the contraption, and pre-heating the catalyist tube there was some white vapors visible coming out of the condenser, but these quickly dissappeared. My guess is that the air already in the system was consumed and only a tiny amount of ethanol was reacted. Hopefully, as i get more time I'll add a fan or fish tank bubbler to get a steady stream of air.

DeusExMachina - 19-12-2002 at 12:46

I didnt have time to read all the posts but I would like to see if this would work for making the acetaldehyde. Someone said that C[sub]2[/sub]H[sub]6[/sub]O and H[sub]2[/sub]0[sub]2[/sub] plus a catalyst will make acetaldehyde.

C[sub]2[/sub]H[sub]6[/sub]O + H[sub]2[/sub]0[sub]2[/sub] + HNO[sub]3[/sub]

DeusExMachina - 19-12-2002 at 12:48

sorry, that post got messed up and I dont know why I can't edit it. I was asking if C2H6O + H202 + HNO3 = C2H4O

solo - 21-12-2002 at 16:45

Here is a recent post on acetoaldehyde synthesis recently posted on the Hive, at

http://www.the-hive.ws/forum/wwwthreads.pl

Captain_Mission
(Stranger / Eraser)
12-20-02 17:50
No 391191

acetaldehyde can be made from acetylene using HgSO4. It´s just a normal alkyne hydration forming an enol CH2=CH-OH, wich isomerises to CH3CHO.

I hope this is a good source.........

no air needed!

Organikum - 28-12-2002 at 15:15

Hey blazter, you don´t have to blow air into the tube and it must not be as hot as most believe. If your copper glows you are far to high with temperature.
I found this nice setup on the net:

The start of the reaction can be seen as the copper in the tube gets brighter.
The hydrogen is catched over water on the left side. Before firing up the burner the EtOH is boiled until you see it condensing in the tube.

And thats it. Thanks to Dr.Blume Germany for this

ORG

[Edited on 13-4-2003 by Organikum]

[Edited on 13-3-2004 by Organikum]

RE: synthesis of acetaldehyde

solo - 10-1-2003 at 21:28

Acetaldehyde may be conveniently prepared by distilling from paraldehyde in the presence of a trace of sulfuric acid; an efficient fractionating column should be used..........solo

trinitrotoluene - 23-4-2003 at 15:01

Today I mixed 10ml of freshly distilled 95% ethanol with 15ml of 30% H2O2 in a 250ml flash. I then shook the mixture, after that I noticed a smell, the smell it a fruit like oder which as described in the book may be some acetaldehyde. I'm not sure how much though.

ethylene glycol - again

Polverone - 30-8-2003 at 12:24

Well, I've again found reference to the preparation of acetaldehyde from ethylene glycol. The first was from The Chemistry of Carbon Compounds (forget full title, multi-volume set). It says that acetaldehyde can indeed be prepared by heating ethylene glycol with dilute H2SO4. Unfortunately, no details were given. The original reference seems to be from a Russian chemistry journal from 1902 - not the most accessible reference. Under the same heading it said that passing ethylene glycol vapors over alumina at 200 C gave a mixture of acetaldehyde and polymerization products.

I found more confirmation in Wheland's Advanced Organic Chemistry (1949), though again details of the experimental conditions are not given. Finally, a recent Tetrahedron Letters article mentioned the conversion of ethylene glycol to acetaldehyde by H2SO4, though the authors were investigating the mechanism with computer simulations so there were again no lab details given.

If I still had ready access to my lab equipment you can guess what I'd be trying this weekend.

most simple and OTC from pyruvic acid

Organikum - 12-11-2003 at 07:37

When you boil pyruvic acid with diluted H2SO4 you get acetaldehyde boiling out of the reaction.
Pyruvic acid is easily prepared from sodium pyruvate available over the net (unsuspicious not so expensive) or at the healthstore (expensive). Stochiometric amounts of HCl should do the trick I guess.

Thats from a 1992 Chembook (for teachers education / university).

This is not the cheapest way but:

Pyruvic acid is also conveniant prepared by biosynthesis - I look this up and post the patent numbers next time plus personal experiences so there is any interest shown.

I prepared DIOXANE several times now from ethylene glycol in very good yields - this solvent is very useful! How to twist this to get acetaldehyde - no clue. For sure simple boiling with H2SO4 gives DIOXANE - and thats fine.

thats a good one isnt it?
ORG

awesome!

KABOOOM(pyrojustforfun) - 12-11-2003 at 20:53

pyruvic acid is the end product of glycolysis. fermentation then use it to make ethanol via ACETALDEHYDE . if we could deactive the last involved enzyme (not sure for name but maybe aldehyde hydrogenaze) ...
alcohol dehydrogenase is a natural enzyme that does the reverse reaction (alcohol to aldehyde)
the condensed chemical dictionary states that pyruvic acid is derivated by dehydration of tartaric acid by distilling with potassium acid sulfate so both decarboxilation and pinacol rearrangement happen in this reaction. just needs wine lees (so fucked, all alcoholic drinks are forbidden here!

)
anyway what about doing the pyruvic acid decarboxilation by distilling its salt with excess alkali in a aqueous sol?

AYY Carumba!

chloric1 - 13-11-2003 at 11:09

KABOOM! Man that sucks no alcohol. I must admit in many ways alcoholism is like a plague here in America but there many more who know how to rationaly use this substance in moderation. HOw better a way to manage high cholestriol than a glass of Pinot just before bedtime

Also, when petrol fuel shortages reach a crisis level we only have our vast midwestern cornfields to turn to to power out generators and automobiles.

As far as acetylaldehyde goes, it looks simple and straight forward and I am anxious to make about 100 ml or so for various uses. I don't know about the availability of the various yeast in Iran but starch can be converted to dextrose by boiling in water acidified with a small amount of HCL. Dextrose is easily fermented to ethanol solution in a few weeks time.

KABOOOM(pyrojustforfun) - 13-11-2003 at 21:29

no problem with alcohol man (I have lab recipe for fermentation and further purification. spirited EtOH is also available ), I was talkin about wine lees as a source of tartaric acid it's probably purchasable where wines are made traditionally. maybe even supermarkets have it. should check ...

another (tough) route to acetaldehyde

Magpie - 13-11-2003 at 22:45

From my 2qtr notes in organic chemistry: Aldehydes can be made from the corresponding alcohol using CrO3*2pyridine complex (Collins reagent). Solvent is CH2Cl2; temp 25 deg C. This has the advantage of not carrying the oxidation too far, which would yield an organic acid. (This is a problem with the Na2CrO7/H2SO4 synthesis, as aldehydes are easily oxidized.) The pyridine serves to "poison" the reaction. Be warned that pyridine is nasty stuff (really sickening odor) and is a carcinogen, I believe. I would recommend having very good ventilation if this is used.
I realize that with all these nasty reagents it would be easier to just buy the acetaldehyde!

Organikum: I like your photo from Dr. Blume. I would have killed for those jacks in organic lab last winter. I also noted the clay tile bench top. In the USA we normally use a 1" thick epoxy resin.

Organikum - 21-11-2003 at 07:18

Torula yeast produces up to 25g per liter of pyruvic acid during his fermentation cycle.
Make the sodium salt in situ as pyruvic acid is hard to isolate - evap, filter wash - HCl, voila - pyruvic acid.

MagPie:
If you use an simple matter-converter acetaldyde is no problem at all. For most here a matter converter is more easily in reach as this famous reagent ya know?

Yes! Dr. Blume rulez!

[Edited on 21-11-2003 by Organikum]

Theoretic - 21-11-2003 at 07:57

From various chemistry books i've seen evidence that copper doesn't act as a simple catalyst. One says that the hydrogen made is absorbed into the copper and then is oxidized by air. The other, among other oxidizing agents that produce acetaldehyde from ethanol, lists CuO at 300 C, so I assume it's much more efficient than simple copper. I guess that the initial "white fumes" were the result of the reaction that happened untill the copper became saturated with hydrogen and all the outer CuO layer was consumed. I assume if the tube was heated strongly enough, the hydrogen would desorb and there would be no problems. Looking at the evidence, I suggest finely powdered CuO in a copper tube (taking no chances).

vulture - 21-11-2003 at 08:46

CrO2Cl2 in CCl4 is another way of preventing oxidation of the aldehyde.

I wonder if CH2Cl2 could be used instead of CCl4.

Please theoretic

Organikum - 22-11-2003 at 04:17

read Marvins and my posts in this thread regarding the difference between "dehydrogenation" and "oxidative dehydrogenation".
This might clear the confusion.
Of course a plain coppertube is a bad catalyst - very good is copper precipated on zink by cementation and oxidising this catalyst first, then reducing it with hydrogen or ammonia to gain copper structural promoted by ZnO.
This is a highly active dehydrogenation catalyst in special for EtOH.

fritz - 7-12-2003 at 13:59

Preparation of K-chromate.
First you have to obtain Cr(OH)3 -but this should be not too difficult! to a suspension of the Cr(OH)3 KOH is added until pH is at 9-11. to this you add 30% Hydrogenperoxide (violent Oxygene generation) H2O2 is added in 10-20ml portions as the O2-generation decreases. (if pH drops add KOH to the mixture) At the end of the oxidation the solution should be yellow and no traces of a green color should remain. The sln is boiled until all O2 is escaped. if necessary it is filtrated. Finally the solution is concentrated by boiling until it´s deeply yellow. now the sln is filtrated hot in the five times of it´s Volume of ETOH. After cooling about 30min in an ice-bath the ppte is filtrated off. The recrystallating step from EtOH may be repeated. The resulting is Potassium-chromate. For the production of acetaldehyde you have to add a sulfuric acid solution of K-dichromate to EtOH. In acid solution chromate forms dichromate. So the only thing you have to do is to increase the amount of sulfuric acid. (I don´t feel like calculating the new ratio right now)

Permanganate in my opinion is bad. I think it would create acetic acid because its oxidizing potential is very high.

The Acetaldehyde which destills off is collected in diethylether. To this sln. gaseous ammonia is introduced and aldehydammonia is formed which could be separated by filtration. this may also be a good possibility for storage of acetaldehyd. To obtain it from the aldehydammonia 25g of this stuff is solved in 25ml water. A (cold) mixture of 30ml sulfuric acid and 40ml water is added and the aldehyde is distilled off.

OYour on to something

chloric1 - 21-1-2004 at 18:33

friotz, I think your on to something there with the aldehyde-ammonia adduct. Would be good for storage. Also, the steps from your chromate sparked a rather important issue. Recycling dangerous goods. If you have trivalent chromium as a by product then you can reoxidize it to reuse it again.

At least here peroxide is sold at health food stores at 35% concentration so I dont think it would be a major problem. Really, our hobby is under close scrutiniy and if at least some of us can show that we are responsible in handling toxic polluting chemicals, them maybe we can regain the freedom to explore our hobby.

blip - 27-1-2004 at 15:44

I was playing around with various chemical equations today during some free time I found, particularly decomposing calcium salts of carboxylic acids. Normally you get aldehydes (HCHO with Ca(OOCH)₂) and ketones (e.g. CH₃COCH₃ with Ca(OOCCH₃)₂). Btw, I chose calcium because CaCO₃ is so readily available to me in the form of... chalk!

Easy to crush up, and all.

I then got into the "double salts" (correct phrase?), such as Ca(OOCH)(OOCCH₃). If this could exist, even in small amounts where distillation would be required, one could theoretically make acetaldehyde via:
CaCO₃ + HCOOH + CH₃COOH > Ca(OOCH)(OOCCH₃) + CO₂ + H₂O
Ca(OOCH)(OOCCH₃) ^D> CaCO₃ + CH₃CHO

If you need HCOOH, you could always use oxalic acid (maybe from Zud cleaner) and glycerin by using this method. This may also be of interest.

re: getting pyruvic acid

Polverone - 27-1-2004 at 23:00

Quote:

When you boil pyruvic acid with diluted H2SO4 you get acetaldehyde boiling out of the reaction.
Pyruvic acid is easily prepared from sodium pyruvate available over the net (unsuspicious not so expensive) or at the healthstore (expensive). Stochiometric amounts of HCl should do the trick I guess.

According to The Old References, pyruvic acid itself is prepared by distilling tartaric acid with KHSO4 at 200-250 C. And potassium hydrogen tartrate is easily available (though a bit expensive) from grocery stores. Find a place that sells in bulk; I can get it for about $13/kg. If bought in a little spice bottle it's probably more like $50/kg. Now you don't need to order from the net or expensive health food stores at all!

Of course, this depends on how pure your acid must be... some old methods leave products that are difficult to purify, or else the yields are bad.

Mendeleev - 4-2-2004 at 12:55

The copper pipe method sounds nice, looks I will be doing some welding this weekend. Why is acetaldehyde in such high demand? Besides making pentaerythritol what uses does it have?

maybe

anubis - 12-2-2004 at 15:33

try also methylation of formaldehyde.
there should be a catalist metal but i dont know which.
bonding two ch its easy tho.
one way might be:
ch3cl + ch2o --ni---> ch3cho

my patience is wearing thin

Polverone - 13-2-2004 at 14:11

Navarone, Navarone's Ghost, Anubis:

Your writing is sloppy, riddled with errors, and provides little of interest even when one ignores its technical blemishes.

I have valuable advice for you:
The next time you post anywhere other than Whimsy, provide enough details to show that you've already investigated the topic you are talking about. The investigation could be an experiment that you have conducted, or that you have seen someone else conducted, or even something that you read in a book or journal or on a reputable website.

Whatever you post about, you should make a respectable effort to spell words correctly and in their entirety, and to use such perfect punctuation and grammar that no 7th grade teacher of English would hesitate to give you an "A."

If you don't post about a technical subject, and don't post in Whimsy, then your prose should be rich and beautiful in addition to technically flawless. If Vladimir Nabokov's ghost isn't green with envy, you have failed.

I hate cluttering up perfectly good threads with this sort of off-topic discussion, so let me be extra-clear:

If you are incapable of following the above advice, kindly go home and eat bleach and die.

Geomancer - 14-2-2004 at 08:10

Acetaldehyde is attractive as a general purpose two carbon synthon. Although I think that the best route would involve simple catalytic dehydrogenation, how about the following?
The problem with simple (electrolytic or chemical) oxidation of ethanol is that primary alcohols are wont to overoxidise. Oxidize boiling isopropanol instead. Pass the vapors up a fractionating column packed with an MPV (Meerwein-Ponndorf-Verley) catalyst. Inject ethanol somewhere in the middle of the column, and remove acetaldehyde from the top. If low boiling azeotropes could be avoided, you get the equivalent of high temperature dehydrogenation without the high temperature.

Organikum: Could you give details and/or references for the ZnO promoted catalyst? What temperature does this stuff work at?

Organikum - 14-2-2004 at 09:35

Reference:
Anorganisch-chemisches Institut der Technischen Universität München
Hochselektive Katalysatoren
zur Gasphasendehydrierung
von Alkoholen
Markus Ludwig Gitter
Teiweiser Abdruck der von der Fakultät für Chemie der Technischen Universität
München zur Erlangung des akademischen Grades eines
Doktors der Naturwissenschaften
genehmigten Dissertation.
A.D. 2002

translated from the text:

Dehydrogenation of EtOH:
Coppercatalysts with ZnO, CoO and CrO3 as structural promotors. The reaction temperature is limited to 270°C - 330°C for to reach a selectivity towards acetaldehyde of 95%.
Yields (per pass) are limited to 30% to 50% this way.
The hydrogen produced as byproduct is clean enough for use in catalytic hydrogenations.

The preparation of the catalyst is a standard procedure for precipitating metal catalysts onto a metal support - I think I got it from some patents. It is tried and true.
(it cost me a damned long time to find out what "structural promotors" means)
If you precipitate copper on zinc you will see that the copper grows on the zinc in form of fractal "trees" providing a huge surface area later in the dehydrogenation. Thats the whole trick of the "structural promotion" of zinc.

A coppertube filled with copper-scrubpads works fine if the amounts of acetaldhyde needed are not to large (less than one liter) - important is to activate the copper by first oxidising it - blowing air through the tube at red dull heat - and reducing it again what can be conveniantly done by passing ammonia or hydrogen through the hot tube.
It actually works also without this activation step. but yields are low.

Mendeleev - 17-2-2004 at 07:54

A bit off topic; I apologize, but how did you know, Polverone, that anubis was Navarone? I saw the ammonium chloride thread where he was a complete ass, but how did you recongnize him as opposed to some other idiot with bad spelling?

thunderfvck - 17-2-2004 at 08:53

Check out the benzyl magnesium chloride thread, you will see. It's in general chemistry (reffering to anubis-navarone shitter).

[Edited on 17-2-2004 by thunderfvck]

Polverone - 17-2-2004 at 14:36

I am good at recognizing writing-styles, at least where a single writer using multiple names does not make a good effort to alter styles between names.

For example, if you search alt.engr.explosives on Usenet for "Rosco P. Coaltrain" or the E&W Forum for "Rosco Bodine," I think you will have found our Mr. Anonymous. The writing styles are very similar and he discusses similar topics. I'm a little bit sad that after finally dropping his cloak of super-anonymity he has not seen fit to post here at sciencemadness.

Oh, and I checked Anubis's signup IP address.

Mendeleev - 19-6-2004 at 11:49

Madscientist, you stated you managed to get 60 mL of liquid once you began to effectively cool the distillate. Can you describe how you arranged your apparatus, was the copper just a straight or did you make a coil for greater heating area?

Mendeleev - 26-6-2004 at 11:30

I gave the acetaldehyde synthesis a try today. I hooked up an apparatus which consisted of a flask connected to a heated copper coil connected to a PVC condenser full of ice, connected to a flask. I started boiling about 550 mL of ehtanol and heating the pipe, and so far there is about 50 mL of distillate, and it has a mild fruity smell, but I am not sure if it is mostly unreacted ethanol or acetaldehyde as they both have the same density. I gave the synthesis a break for now because I noticed smoke coming back into the distilling flask. It was really weird it looked like when dry ice sublimes, it was pretty dense smoke because it came back out of the hose and fell into the ethanol, I thought this might have been my acetaldehyde going in the other direction, but I am not sure.

froot - 26-6-2004 at 12:22

I also tried the heated copper method not so long ago. I used a 500ml boiling flask with about 1m of 3mm copper tubing. The tubing ran from the stopper down to a coil around the bottom of the flask so that when on a gas cooker both the coil and the flask were being heated. The receiver was in a bowl of ice.
I brought the ethanol to boil and collected the product which smelled mostly like ethanol with a slight fruity aroma or maybe that was just imagination?!?
I see 3 main perameters that can be tweaked here:
1) The copper temperature.
2) The Ethanol temperature.
3) The length, size, and configuration of the copper tubing.

Organikum - 30-6-2004 at 02:55

Plain copper tubing will not work well. Prepare a catalyst as described - it is easy like shit or at least use a tube filled with copper scrubbing pads.
But hey - precipitating copper from the sulfateor better chloride is not rocket science.

Rosco Bodine - 29-9-2004 at 12:16

Quote:

Originally posted by Polverone
I am good at recognizing writing-styles, at least where a single writer using multiple names does not make a good effort to alter styles between names.

For example, if you search alt.engr.explosives on Usenet for "Rosco P. Coaltrain" or the E&W Forum for "Rosco Bodine," I think you will have found our Mr. Anonymous. The writing styles are very similar and he discusses similar topics. I'm a little bit sad that after finally dropping his cloak of super-anonymity he has not seen fit to post here at sciencemadness.

Cheer up friend . Sorry for being cryptic , but it seemed prudent for some topics with folks like idefense and their echelon buddies lurking about . Anyway , we all have some sort of alias on the web , or else my name is not Rosco P. Coaltrain :cool:

My IP is as certain to be a fib too

so I hope the logins here are not IP specific

true_alchemy - 29-9-2004 at 17:04

NaOCl (5%-bleach) in acetic acid, I believe, is a nice clean reaction for ketones from sec-alcohols. It's been 14 years since I have done it but if I recall it works for aldehydes as well. ie ethanol added to clorox in acetic acid @ 20-30C. Clean up is done with sodium metabisulfite to kill excess bleach. There are textbook procedures for this on the web.

[Edited on 1-10-2004 by true_alchemy]

tom haggen - 21-5-2005 at 10:34

I was just wondering about the method using H2O2 , EtOH, and a KMnO4 catalyist. Would you first add the KMnO4 to the EtOH, and then set of for an addition reaction by putting your H2O2 into an addtion funnel. Also are you going to have the acetal, and ethonal by products that megalomania's method has? Can you bubble ammonia gas through your crude product to get aldehyde-ammoina?

S.C. Wack - 21-5-2005 at 11:42

Page 4686 of JCS (1956) claims a 50% yield by reflux of EtOH with excess MnO2 for 20 min. No explicit experimental is given in this case. A number of aldehydes and a few ketones are prepared, but my copy (from microfilm) is of poor quality.

[Edited on 21-5-2005 by S.C. Wack]

garage chemist - 21-5-2005 at 11:47

When I added 5ml ethanol to 50ml bleach (2,8% NaOCl), no chloroform was produced, but it still got warm and a strong fruity smell was being given off. I'm sure that a considerable quantity of acetaldehyde had formed.
On addition of HCl, the smell got much more intense and the solution started boiling even though it was only mildly warm.
You know the boiling point of acetaldehyde?
I think this could be made into an economic method, because the precursors are so cheap and easy to get.

chemoleo - 21-5-2005 at 19:52

The density of acetaldehyde is 0.783, the melting point - 123.4 deg C, and the boiling oint at 20.2 deg C. so volatile, although that is bound to be different in aqueous solution.

I am not sure about this being a good route. I remember doing oxidation experiments with H2O2, and the smell was definitley there, but it's hard to separate the aldehyde from the rest.

What I always wanted to do was to react acetylene with H2O in the presence of mercury salts, according to
HCCH + H2O --> CH3CHO

This is how it's done industrially. Shouldnt be impossible to do and the purity should be good, no ethanol contamination or anything else for that matter.

Kalle anka - 10-6-2005 at 06:45

Man! You guys must have written essentially all methods possible to make aliphatic aldehydes. But what comes to novel reactions here is something that may be of some interest for you crazy people out there!

Now talking about acetaldehyde i want to tell you about an experiment of mine. One night i dreamt about several things but i woke up when it crossed my mind. I wanted to make copper salts from metallic copper but as you guys know its reduction potential is higher than hydrogen, ie. acids wont bite on it. A classical example in vitually all inorganic chems books i've seen is the demonstration of HNO3 as an oxidising acid. I have no access to HNO3 nor H2SO4, so the reason i woke up suddenly was that i realised (omg im a n00b) that the NO3 ion is reduced.

My point is that i oxidised metallic copper which i took from some net cords and other cables with NaNO3 and HW grade 30% HCl. It needed some external heating to start but then proceeded with a violent continuous exhaust of NO2 which settled as a reddish-brown toxic fog on the floor

Later i dreamed i wanted to see if i could do something else so i just grabbed what we here in Sweden call "spolarvätska", dont have the english word for it but it is a solution of ethyl alcohol in water which is used in the cars to rinse the main window. You could use any other available ethyl alcohol for this purpose.

Anyway, as the relatively bearable chlorine like smell of NO2 could not have been enough, this shit made an awful pungent strong f*cking apple odour even in my dream, which took a hell of a long time to exit. No appetite for apples

As i made this in a ordinary 250ml rbf, all shit boiled off from the warm (~80*C) NaNO3+HCl solution and really just gave me a bad day. If i really wanted to look at this possibility to make acetaldehyde, i would have set up a distillation apparatus and added 96% ethyl alcohol through a claisen dropwise to the warm solution of HCl and NaNO3. I would also have liked to keep water through condensor cold and possibly placed the reciever in an ice bath. But until then i think i just wake up and do something constructive.

Take care and have fun

Sandmeyer - 10-6-2005 at 11:06

Quote:

Originally posted by Kalle anka
Man! You guys must have written essentially all methods possible to make aliphatic aldehydes. But what comes to novel reactions here is something that may be of some interest for you crazy people out there!

Now talking about acetaldehyde i want to tell you about an experiment of mine. One night i dreamt about several things but i woke up when it crossed my mind. I wanted to make copper salts from metallic copper but as you guys know its reduction potential is higher than hydrogen, ie. acids wont bite on it. A classical example in vitually all inorganic chems books i've seen is the demonstration of HNO3 as an oxidising acid. I have no access to HNO3 nor H2SO4, so the reason i woke up suddenly was that i realised (omg im a n00b) that the NO3 ion is reduced.

My point is that i oxidised metallic copper which i took from some net cords and other cables with NaNO3 and HW grade 30% HCl. It needed some external heating to start but then proceeded with a violent continuous exhaust of NO2 which settled as a reddish-brown toxic fog on the floor

I don't get it, what did you make?

Organikum - 11-6-2005 at 01:46

He dropped copper oxide into denat. alc. and got some apple like smell.

chemoleo wrote:

Quote:

the smell was definitley there, but it's hard to separate the aldehyde from the rest.

And thats exactly the point. We have a trillion easy methods to produce an apple smell from alcohol - actually about anything what hase some oxidising properties does this. But one gets no acetaldehyde as the the smell seems to be present with minute amounts of aldehyde already in special when this is in solution.

Woth to mention might be that the cinnamaldehyde decomposition with bases produces equimolar amounts of benzaldehyde and acetaldehyde.

Kalle anka - 14-6-2005 at 15:05

damn it.. i saw that the Hcl + NaNO3 mixture was a good oxidiser mixture. when NO3 oxidzes something its reduction potential is 0.96V, lower than Cr2O7, ie. its a weaker/milder oxidiser than dichromate.

I added ethanol to this mixture and got the damn acetaldehyde that is the topic of this thread geezers! What else with an apple like odour could i've made that would fit under this topic?

Organikum - 15-6-2005 at 03:59

As told before: Some acetaldehyde was produced - this is easy. But I doubt that it was produced in reasonable amounts.

Separate - measure.
Apple smell is already present with traces of acetaldehyde and it is no prove at all.

By now you have not made acetaldehyde but a mixture with an apple like smell.

/ORG

vulture - 15-6-2005 at 13:18

The main problem with the production of acetaldehyde from ethanol is that when you use water as a solvent, you're always wasting aldehyde by conversion to acetic acid.

The easiest solution to prevent this is using aprotic polair solvents, but they are usually expensive, hard to get and/or toxic/nasty.

Now, a suspension of CrO3 in aceton is being used in the Jones-oxidation, this might be interesting. Solid CrO3 embedded in graphite can also be used to specifically convert alcohols to aldehydes (Lalancette reagent).

Maybe CrO5 in ether solution is also an option, but this would require caution, as it is a very powerful oxidizing agent.
Separation of ether/aldehyde would also cause problems.

[Edited on 15-6-2005 by vulture]

12AX7 - 15-6-2005 at 16:28

Quote:

Originally posted by vulture
Maybe CrO5 in ether solution

Decavalent?

Hm, not really sure what else you meant... CrO3 is the highest valence anhydride (or rather Cr2O6) I'm aware of.

Edit: I'll be darned, you can isolate perchromate?

Tim

[Edited on 6-16-2005 by 12AX7]

vulture - 16-6-2005 at 12:10

No, hexavalent. It contains two peroxogroups.

Sandmeyer - 16-6-2005 at 13:03

Quote:

I added ethanol to this mixture and got the damn acetaldehyde that is the topic of this thread geezers! What else with an apple like odour could i've made that would fit under this topic?

I don't know, I never smelled acetaldehyde. Btw, did you purify/isolate it, what was the yield? Unless these detais are known your post is meaningless.

[Edited on 16-6-2005 by Sandmeyer]

chloric1 - 16-6-2005 at 13:14

Quote:

.

I am not sure about this being a good route. I remember doing oxidation experiments with H2O2, and the smell was definitley there, but it's hard to separate the aldehyde from the rest.

I hear ya but what about separation with concentrated bisulfite solution? This should isolate most small molecule carbonyls from alcohols and the like. THen you only need to add some dilute sodium bicarbonate or HCL to break down the bisulfite.

Rosco Bodine - 16-6-2005 at 14:21

Anyone having vanadium pentoxide on hand might try adding hydrogen peroxide
to a stirred suspension of the vanadium pentoxide in warm ethanol . I'm thinking
pervanadic acid might form in sufficient amount to oxidize the ethanol to acetaldehyde which should volatalize as it is formed . The vapor could be condensed
and the acetaldehyde isolated as a liquid , or the vapors could be conducted directly to whatever subsequent reaction where the acetaldehyde is needed and introduced through a bubbler or dispersion tube .

Here's a link for a similar reaction .

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMe...

I found a citation for a journal reference regarding the production of acetaldehyde from ethanol by vanadium peracid . This journal article should be given a look , perhaps added to the literature request list .

Conte, V.; Di Furia, F.; Modena, G. J. Org. Chem. 1988, 53, 1665

EDIT : It appears that the citation was in error and the more needed reference is an earlier article by the same researchers found here :

Bortolini, O.; Conte, V.; Di Furia, F.; Modena, G. Nouv. J. Chim. 1985, 9, 147-150

The JOC article is only a followup relating to the production of acetone from isopropanol . But the original article describes the details for the reaction conditions , and the production of acetaldehyde from ethanol . The pertinent
reference is likely in Italian , so translation
will be needed if an English version is not
already a parallel publication .

Evidently there is an English version of the journal , published as

" New Journal of Chemistry "

[Edited on 17-6-2005 by Rosco Bodine]

ordenblitz - 1-7-2005 at 18:39

After reading about oxidation of alcohol with H2O2 using V and Mo as catalysts, I decided to give it a try.
First I did a few small experiments in test tubes to see what effect different catalysts had on peroxides ability to oxidize ethanol to acetaldehyde. It was suggested that simply adding a catalyst to the mix such as KmNO4 forming O2 and possibly nasent O might do the trick.

I made a simple mix of 50ml of 95% ethanol and 50ml of H2O2 50%. I split this equally into 4 test tubes.
To the first I added ~.01gm V2O5 - there was a slight reaction that subsided in a few seconds to a stable solution.
To the second, four 1mm platinum catalyst beads. - there was immediate evolution of O2 that continued is a stable manner.
The third ~.005gm KMnO4 - a fairly rapid evolution of O2 began and at one point rose up in the tube but then settled down to a constant fizzing.
the fourth ~.008gm MnO2 - same as #1

These were loosely capped and left to sit for 2 hours. After uncapping there was only the scent of ethanol in #2 and #3. In #1 and #4 there was a strong smell of CH3CHO. I seriously doubt the simple mixing of H2O2 and CH3CH2OH. Even with the addition of something like KMnO4 or MnO2 to cause the H2O2 to decompose probably would not form any appreciable quantities of aldehyde.

Experiments with V2O5:

96ml C2H5OH and .1 gm V2O5 and a few teflon boiling stones were placed in a 500ml 3 neck flask equipped with an addition funnel, thermometer and a jacketed condenser set for reflux then connected to a Graham condenser being cooled with 5º circulated water leading into a receiver cooled in an ice bath.
http://img80.imageshack.us/img80/650/setup1by.jpg
100 ml of H2O2 50% was placed in the addition funnel. 25 ml of peroxide was slowly added to the alcohol V2O5 soln dropwise as the flask was being warmed. At about 40~ the liquid began a slight boil.
http://img80.imageshack.us/img80/2905/startofrxn2tx.jpg
After temperature reached 50º the mantle was shut off. The temperature continued to rise and the liquid began a medium boil at about 60º. At this point a distillate started coming over slowly and the top of column was reading ~25º. H2O2 was again added in about the same rate as the distillate was coming off. I kept cold tap water flowing through the reflux in an attempt to keep the reaction under control. When the temperature went over 80º, I pulled out the mantle and set the flask on rings and began to flush the outside with tap water to throttle the thing back.
http://img80.imageshack.us/img80/2406/runaway5vi.jpg
This reaction continued for about another 1/2 hour with continuos cooling both in the column and on the outside of the flask. All the peroxide was in by now. Meanwhile the temperature at the head of the column was held below 40º as best as possible. The vigorous action began to slow. At this point the mantle was put back in the game to keep the reflux going as I thought there might still be some unreacted ethanol. Even with additional heating the thing was still slowing down and some interesting color changes happened.
http://img80.imageshack.us/img80/787/yeltored3eo.jpg
Then back to yellow with a tinge of green.
http://img80.imageshack.us/img80/5606/yelgr21yy.jpg
And finally to green after she was tired out.
http://img80.imageshack.us/img80/8018/green9kj.jpg

After distilling the product once more, coming over at 21º to 23, final total was 18 grams of acetaldehyde as confirmed by FTIR. Also something I didn't expect, in the higher boiling fraction of the original distillate was found ethyl formate.
http://img80.imageshack.us/img80/66/ethform7zu.jpg

I also ran the green leftovers and found more ethyl formate as well as ethyl acetate. Which makes sense as it smelled strongly of acetic acid.

I have tried this reaction now 3 times.
The first as above by adding the H2O2 slowly to the mix of C2H5OH and V2O5.
The second, I tried adding the EtOhV2O5 to the warmed H2O2 in the flask. And third carefully mixing the V2O5 with the H2O2 before and then adding to the flask,
http://img80.imageshack.us/img80/2408/mix2zd.jpg
warming then slowly adding the EtOh. All in all it was about a draw, with the best yield in the 3rd setup of a whopping 28.02gm of product. I think I wouldn't do this method again.

Final note:
I did do this reaction a fourth time, similarly to the third run above but in the H2O2/V2O5 mix I added about 3ml of Hcl in an attempt to lower the ph and improve the yield. What I got was a yield of possibly something else…The FTIR said it could be "methyl vinyl ether -alt- maleic acid mono ethyl ester" Or the pic below… it says only a fair match but to be sure that sample was destroyed immediately!!!

[Edited on 2-7-2005 by ordenblitz]

C10H14ClN.JPG - 23kB

12AX7 - 1-7-2005 at 20:31

FYI, you can take screenshots by pressing the PRINTSCREEN button then pasting in your favorite image editor.

Tim

Rosco Bodine - 1-7-2005 at 21:29

Interesting experiment !

The yellow to red color is pervanadic acid ,
or perhaps an unstable ethanol pervanadic acid complex .
That colored intermediate is consumed in the oxidation of the alcohol and then regenerated by the reaction with the incoming hydrogen peroxide . It is possible that if additional ethanol and hydrogen peroxide were simultaneously added in correct proportions to the warm red mixture at the correct temperature, the reaction may possibly continue steadily at a rate regulated by the speed of the addition , until a point of dilution by accumulating water from the H2O2 quenches the reaction . How far it might continue would depend on the concentration of H2O2 being used .
The ratio of acetaldehyde to higher oxidation products likely decreases with
temperature , so the yield may increase
running the reaction at the lowest acceptable rate where the reaction still proceeds . The amount of catalyst in
the mixture may also have some bearing .
There is likely an optimum concentration for a given temperature and reaction rate . Buffering the reaction mixture
is another possibility if a particular pH favors the oxidation for acetaldehyde .

Anyway , the use of pervanadic acid looks like a valid method for acetaldhyde , for those not inclined to go the route using tube furnaces .

The_Davster - 1-7-2005 at 23:19

Your 95% etOH being denatured with methanol would explain the ethyl formate. Just having the methanol being oxidized to formic acid then undergoing an esterification reaction with the ethanol.

Interesting experiment.

[Edited on 2-7-2005 by rogue chemist]

Rosco Bodine - 2-7-2005 at 00:45

28 grams of acetaldehyde from 96 ml ethanol is a 39% of theoretical yield .

Definitely on the right track and yield could probably be increased considerably with some variations on the temperatures and probably the pH .

Perchromic acid should behave similarly ,
and may be a bit less active so it may be worth trying if overoxidation is in part responsible for the low yield via pervanadic acid oxidation .

That New Journal of Chemistry article may shed some light on the reaction conditions which are most favorable .

I know that sodium dichromate solution acidified by gradual addition of dilute sulfuric acid can also be used for the oxidation of different materials to aldehydes . I wonder if such a chromic acid solution could not be enhanced to function as a perchromic acid regenerating
reagent simply by gradually adding hydrogen peroxide to the reaction mixture . A much smaller amount of dichromate and sulfuric acid could be used simply to start the reaction , since the peracid regenerates .

ordenblitz - 3-7-2005 at 16:23

12AX7,
Thanks for that suggestion. It will save me time screwing around with the camera. I am a Mac guy and don’t know all the cleaver pc stuff.

Roscoe,
You are right on target about the color changing with the amount of H2O2 present. I tested this with some spent remains and was able to easily change the dark green color back to dark red then back to reddish yellow again. One would need only to reduce the water and begin again. I did some small scale tests again today, adding drop wise, H2O2/ethanol mix to V2O5 in a slight amount of etoh. The reaction is more controllable. One needs only to be able to cool the reaction to hold about 40deg., if it goes much higher and you can really detect acetates being formed. The reaction is fairly slow at 40 though and it might take multiple hours to complete. I would like to explore your perchromic idea further; I think it’s a good one.

Rogue chemist,
I used grain alcohol so there should have been no methanol present. I was puzzled by the formate as well.

Rosco Bodine - 3-7-2005 at 17:21

Probably to get the best yield of acetaldehyde may require operating the reaction just warm enough for the catalyst to stay in active regeneration ,
and also boil off the acetaldehyde . The temperature for regeneration activity is probably going to be the limiting factor ,
and that will be the parameter where the concentration of the catalyst will be a real factor in optimizing the conditions for acetaldehyde . I think that once the right conditions are found , the reaction could be set to run at a steady but slow rate ,
moderated by a shallow depth of flowing tap water , which is a fairly constant temperature , and then control the reaction at some drops per minute count found to keep things " in the groove " so the reaction could run unattended and
deliver the acetaldehyde to a receiver bottle in a styrofoam ice bucket . An old IV pump would really be ideal for this reaction , as you could run separate metered feeds of alcohol and H2O2 .
With a digital temp sensor and a parallel port on the IV pump , you could write a little control program and have the PC babysit the reaction as process controller ,
rate regulator type of setup . Put the entire apparatus in a footlocker with wheels and you have a portable acetaldehyde factory

Add a few extra reaction lines and another reaction chamber with some formaldehyde and lime , and the box will be shitting pure pentaerythritol everywhere it goes

You'll have to keep behind it with a shovel to keep it from getting too deep

mantis - 20-7-2005 at 11:10

A good and clean way to produce acetaldehyd is the oxidation of lactic acid by H2O2:
CH3-CH(OH)-COOH+H2O2 ---> CH3-CHO+CO2+2H2O
To have a faster reaction you can heat it up a bit.
When you boil lactic acit you get a mix of acetaldehyd and formic acid. As cat. you can use sulphuric acid.
CH3-CH(OH)-COOH cat. or heat--->CH3-CHO+HCOOH

[Edited on 20-7-2005 by mantis]

HCCH + H2O to CH3CHO

ordenblitz - 7-8-2005 at 16:39

I have been wanting to get the time to try production of acetaldehyde by passing C2H2 through a dilute solution of H2SO4 containing a small amount of HgSO4. Today I took the time.

105 ml. H2O
15 ml. H2SO4 96%
0.5 gm. HgSO4

Were mixed together and placed in a 250 ml. kjeldahl flask and warmed in a water bath to 60 deg C
In the flask was placed a fine glass airstone bubbler fitting with exit jacket. I connected the outlet via hose to a cooled graham condenser that lead into a collection flask. A commercial welding acetylene tank was connected through the regulator to the airstone inlet.

After opening the tank and starting the gas flow slowly, very soon a strong acetaldehyde smell could be detected coming from the collection flask. It was very strong and somewhat dissimilar to the smell I am used to from the CH3CHO made from ethanol. Usually you end up with a mix and get the smell of both.
If I ran the gas in strongly, I could also smell the C2H2 but when running it slowly all I could smell was the sweet strong stink.

Ok I thought, we are off to a good start. So I turned the chiller flowing through the condenser down to 5C and waited.. and waited.. and waited! Come on dammit, could I just get one stinking drop? Nope!

I also discovered that this reaction is exothermic. You only have to get the temp up to 60 before starting then you need to apply cooling. I let the temperature rise to 80 in the beginning and the production of acetaldehyde ceased. I wasn’t aware that I would need cooling.

Ok so this method definitely works but…. You need a big reaction chamber, at least a very long column and a lot of contact area. You have to be able to move a lot of gas to make a small amount of liquid. My bad as I didn’t take the time to crunch the numbers on this before starting. To make this workable for lab scale production I am guessing you need a column maybe 8 cm in diameter and possibly 1 to 2 meters in length.

Sorry, no pics today as I forgot to charge my cam batteries.

[Edited on 8-8-2005 by ordenblitz]

praseodym - 8-8-2005 at 23:30

Acetaldehyde can also be prepared by oxidising EtOH or from acetic acid by dry distillation of calcium acetate with sodium formate, i think.

froot - 9-8-2005 at 08:34

I found out after many attempts that the setup for making acetaldehyde is crucial. In my case I used the ethanol method but the condensing appauratus should be similar.
The only time when I got results was when I set up my condensor vertically as in reflux mode. I let normal cold tap water run through the jacket.
From the condensor ran a 8mm nb tube of about 2m length through a bucket of water full of ice. The receiver was also kept in ice.

I feel it is imperative that the vapours leaving the reaction are chilled properly. I used the condensor in upright position to aid chilling and remove any water vapour before the acetaldehyde is precipitated.

I thought this might help with your acetylene method.

DeAdFX - 10-5-2006 at 20:08

Quote:

Originally posted by Polverone
According to The Old References, pyruvic acid itself is prepared by distilling tartaric acid with KHSO4 at 200-250 C. And potassium hydrogen tartrate is easily available (though a bit expensive) from grocery stores. Find a place that sells in bulk; I can get it for about $13/kg. If bought in a little spice bottle it's probably more like $50/kg. Now you don't need to order from the net or expensive health food stores at all!

Of course, this depends on how pure your acid must be... some old methods leave products that are difficult to purify, or else the yields are bad.

Could other HSO4- salts be used such as ammonia or is potassium the only salt that will work?

Im guessing potassium tartrate and sulfuric acid would work too?

The hydration of acetylene.

markgollum - 6-6-2006 at 15:01

ordenblitz, the temperature that you used for the hydration of acetylene was far to hot!, yields drop to below 50% at temperatures above 50degC.

If I were going to try this route to acetaldehyde I would use the method where the catalyst is a moist paste of sodiumbisulfate and HgO (reacts to form the sulphate).
The advantage of using this catalyst is that the acetaldehyde produced is polymerized to paraldehyde in the reaction flask and later poured off. (see the pages I scanned)

markgollum - 6-6-2006 at 15:04

Sorry, I forgot the attachment.

[Edited on 6-6-2006 by markgollum]

edit (

I can't seem to add my attachment, I guess 1.55MB (6 pages) is to much?,

. )

[Edited on 6-6-2006 by markgollum]

Elawr - 6-6-2006 at 18:01

Apple like smell?... reminds me of high-school chem lab when we prepared simple esters. Really intense fruity smells of various kinds that lingered for weeks, it seemed. Could your reaction have oxidized some of your Etoh to ethanoic acid? What does ethyl acetate smell like?

12AX7 - 6-6-2006 at 18:15

Quote:

Originally posted by Elawr
What does ethyl acetate smell like?

Not far from ether I'd say. Maybe more, er, "body" or something, but I don't associate it with any particular fruit or anything.

Tim

stoichiometric_steve - 6-6-2006 at 23:25

Quote:

Originally posted by 12AX7

Quote:

Originally posted by Elawr
What does ethyl acetate smell like?

Not far from ether I'd say. Maybe more, er, "body" or something, but I don't associate it with any particular fruit or anything.

Tim

sometimes cantaloupe melons smell like ethyl acetate.

Acetaldehyde

CycloKnight - 7-6-2006 at 12:28

There is another route to acetaldehyde that I didn't see mentioned in the posts above.
This is the method used here:
http://www.sciencemadness.org/talk/viewthread.php?tid=2223&page=4

...to convert cinnamaldehyde to benzaldehyde.

Acetaldehyde is the main byproduct produced in that process.
Read psychokitty's post in the link, it contains a quote from the patent and also mentions the acetaldehyde formation.

The attachment

markgollum - 7-6-2006 at 13:34

I re-scanned the pages on the lowest quality setting and am now at 560Kb so it should work this time.

Attachment: The Hydration of Acetylene.pdf (556kB)
This file has been downloaded 411 times

Zinc - 30-6-2006 at 13:03

Be careful when working with acetaldehyde. It is a probable carcinogen.
http://en.wikipedia.org/wiki/Acetaldehyde

JohnWW - 30-6-2006 at 17:25

If it really is a "probable carcinogen", then everyone who drinks alcohol is at risk, because it is an intermediate degradation product of ethanol. I do not think so.

guy - 30-6-2006 at 17:46

That's probably why drinking IS bad for you.

http://www.reboundhangover.com/acetaldehyde.htm

Rosco Bodine - 1-11-2006 at 18:26

Update :

Found an interesting old German acetaldehyde patent that
needs translation to English ....if anyone would be
so kind .

[Edited on 2-11-2006 by Rosco Bodine]

Attachment: DE422729 Acetaldehyde in 90+% Yield via Air Oxidation of Ethanol using Silver Wire Catalyst.pdf (69kB)
This file has been downloaded 264 times

Rosco Bodine - 1-11-2006 at 22:32

And for electrolytic oxidation of ethanol to acetaldehyde ,
the yield is quantitative when the electrolysis is carried
out with the voltage limited to the range of 1.3 to 1.66 volts using a platinum anode . See the attached page .

Perhaps another anode material might work adequately well .

Both of these references are from publications in the
ScienceMadness Library .

Attachment: Page 60 from electrochemistry_of_organic_compounds.pdf (435kB)
This file has been downloaded 272 times

fractional - 2-11-2006 at 04:27

@ Rosco Bodine
Et voilá, the English translation...

I don't think that this process is more interesting than the standard one using copper-wire/ copper-mesh as catalyst.

This method seems not to get many favourable reviews, but I think it is perfectly reasonable once an important modification is applied: External heating of the copper-catalyst with e.g. a bunsen-burner in order to kick-start the reaction is clearly not practicable on any but the smallest scales, but one can also use the copper wire as direct heating element by passing an electric current through it. This ensures an equal and controlled heating of all the copper surface.

The setup to use is a pipe with a spiral of copper-wire inside that's connected to a low-voltage power supply with sufficient current to bring the wire to red heat. The Volts/Amps rating of course depends on the length and the thickness of the wire used.

Attachment: Method for the Production of Acetaldehyde from Ethanol.pdf (11kB)
This file has been downloaded 326 times

Rosco Bodine - 2-11-2006 at 07:54

@fractional

Thank you for that translation .

Silver has such a pronounced catalytic effect on the
oxidation of ethanol selectively to acetaldehyde , it
makes me wonder if a silver or silver oxide anode may
have similar value in an electrolytic cell .

Also concerning the value of silver and copper both as
contact catalysts for the air oxidation of ethanol at elevated temperature .....

the old German patent encourages an idea which I have been considering for an experimental method and catalyst which could be useful for the oxidation of ethanol to acetaldehyde .

There is a familiar example in many chemistry books
about how metallic silver will precipitate from a solution
of silver nitrate upon a piece of copper wire immersed
in the silver nitrate solution .

And there are also methods for the precipitation of metallic copper from solutions of copper salts using organic reducing agents .

While researching refractory materials I came across a
high fired granular porous clay material which is used
as an artificial soil for aquatic plants in decorative ponds
and aquariums , as a substitute for ordinary gravel ,
and it occured to me that this might make a useful carrier
for a catalyst . A similar material is a porous alumina
which is used in water filtration as a substrate on which
grow beneficial bacteria and algae , and this ceramic
could be broken up into granules using a hammer , and
the granules could also be useful as a porous substrate
for carrying a finely divided catalyst .

http://www.drsfostersmith.com/product/prod_display.cfm?pcatid=5073&...

This sort of ceramic filter media is available in different
molded forms from aquarium suppliers and probably
pet shops .

The idea for the catalyst carrier is to agitate the granulated material violently in a copper salt solution
as reduced metallic copper is being precipitated into the pores and onto the surfaces of the granules . And then
subsequently to agitate the copper bearing granules
violently in a solution of silver nitrate so that metallic silver is also deposited . The granular material is then
dried and poured and tamped inside a long copper tube ,
whose inside walls may also have been silvered by
filling the tube previously with silver nitrate . Alternately the copper bearing granules might be placed in the copper tube first , and then the assembly silvered by circulating silver nitrate solution through , depositing
the metallic silver on the granules and the inside walls
of the copper tube simultaneously . Afterwards the
catalyst filled tube is spiral wrapped into a coil but having
a conical form , as if it were coiled around the outside of
a funnel being used as a form for the winding . This
funnel shaped coil can be inverted above a single burner
on something like a gas hotplate or camp stove burner ,
so that the entire coil catches the heat from the one burner , distributed across a considerable length of
catalyst filled tube which forms the coil , having its free ends brought horizontally away by some distance to provide cooled sections as intake for the alcohol and air vapor and exhaust of the acetaldehyde to a separate
condenser .

An aquarium pump could supply the airflow to an airstone
at the bottom of a column of ethanol , and the richness
of the entrained vapor in ethanol could be varied simply
by warming or cooling the ethanol through which the air is bubbled . A three way needle valve manifold as is
used on aquariums for balancing the airflow between separate airstones could be used for achieving a proper mixture , if it was found necessary to blend the vapors
from the ethanol evaporator with additional plain air .

The acetaldehyde vapors exiting the catalytic section
could be initially cooled in a coil air condenser , and then
in a water cooled coil section , then ice water cooled
section , and finally captured by bubbling through an
airstone into icewater in a column cooled by an ice salt bath .

Regarding your suggestion to use electrical heating of
a copper coil , it presents difficulty due to the enormous
current which would be required for causing copper to
get hot from IR heating . What would be required is
some sort of inductive heating of a shorted loop , as
if it was a stalled motor armature and the field coil would be a substantial endeavor . If a copper coil was
to be used , it would be easier to wrap it around some
sort of sheathed cylindrical heating element , and let
the isolated nichrome element in the core do the job of
heating the copper .

An idea that just occurred to me is related to that copper braided sleeve material woven of fine wire that is used as the outer conducter in coaxial cable . That braided copper
sleeving could be silvered by immersion in silver nitrate ,
and it would probably work beautifully inside a copper tube
loosely filled with parallel pieces of the braid . Alternately
the braid could be cut in short lengths and pushed inside
the open end of the tube by the end of a dowel , like
pushing wads into a muzzle loaded rifle using a ramrod .
Silvered copper may work fine as a catalyst , providing
the greater economy of the copper as a substrate for the
silver which has greater activity and efficiency .

Tinned copper braid is commercially available , and it may just be that silvered copper braid is also available , and if so it could be used directly . I know that silvered copper wire
is manufactured , so it seems logical that somebody is probably weaving copper braid using silvered copper wire ,
for use in some high end coaxial cable or other application .

[Edited on 2-11-2006 by Rosco Bodine]

fractional - 2-11-2006 at 09:44

I fear I have not been clear enough before: the copper wire is the actual heater, it is not heated by some external source with which it must exchange heat energy by radiation. The currents needed to heat it up to red heat are not all that outrageous for a typical application. I have done some back of the envelope calculations:

Used PC power supplies are great and dirt-cheap power sources for low voltages and high Amps. Let's assume one rated at 5 Volts, 20 Amperes. The external resistance needed to draw the rated current at the rated voltage is 5V / 20A = 0.25 Ohms.

A copper wire with a diameter of 0.5mm has a resistance of about 0.0876 Ohms per meter. The length of this wire needed to give 0.25 Ohms is 0.25 / 0.0876 = 2.85 meters. This length of wire can be easily fitted as a kind of spool or bobbin inside a reasonably-sized (glas)-pipe.

Let's calculate the expected temperature of this spool operated at 20 Amperes: This depends on the surface area of the wire-assembly (l=2.85m, dia=0.5mm), which is 0.0045 square-meters. It also depends on the emissivity epsilon, which is 0.13 for polished copper (from published tables of materials properties).

The temperature assuming radiative heat transfer only (which is of course a major simplification) is given by Stefan-Bolzmann's law:

Texp4 = q / (Sigma*epsilon*SurfaceArea) + Tenv exp4

T is the temperature of the wire in Kelvin, Tenv is the environmental temperature in Kelvin. q is the power, sigma is Bolzmann's constant (5.67051exp-8).

When you put in the numbers q=100W, Tenv=20 degC = 293 Kelvin, SurfaceArea = 0.0045 m2 the expected temperature of the wire is 1318 Kelvin or 1045 degC, which is actually way beyond red-hot.

Of course there will be losses in the system by conduction and convection, so the temperature will be lower, but I think this is a good starting point, and I think it shows that such a system is feasible.

I have read with interest your ideas about producing a copper catalyst-bed with a high surface area. I am not sure, however, if this will really help for the specific purpose of producing acetaldehyde. The main point of the German patent is that too finely divided silver makes the reaction too violent and reduces the yield, so that "more compact" forms of the catalyst should be used, so I think that the compact form of copper wire should do the trick nicely.

I have not tried this out yet, because I am currently trying to oxidise ethanol using TCCA, with limited success so far (yield 1ml of acetaldehyde using 60ml of ethanol...). If this turns out to be a no-go I will come back to this copper-wire method.

Rosco Bodine - 2-11-2006 at 10:03

I have been doing too many ammeter shunt calculations lately and handling too large conductors ....losing perspective

Of course you are right , and coiling
the element like a long spiral spring would allow for
even larger wire to be used . If this was wound upon
a solid rod and placed inside a glass tube , the vapor would be forced the travel the spiral groove and
would get very good contact and intermixing in
the reaction zone .

I still think that using silver plated copper may have advantage , as the reported yields for the silver are
much higher than for copper alone , in the references
which I have seen , the yield reported for silver is
increased by 50% over that gotten for copper in
a single pass oxidation .

Also I found that the silvered copper braid material is indeed available in various sizes . Alpha wire products
is one of the suppliers .

http://www.electrospec.com/alpha/product_list.asp?c1=05&c2=0505&c3=...

The silver plated tubular braid material is available down to
1/16" ( 1.6 mm ) size , and depending on the cross sectional
area of the conductors , this may also be within reach for
electrical heating if it was used as a coiled element .

BTW , I didn't do the calculations , but just off hand it would
have been my guess that about 400% or even much more current would have to be put through that nearly 3 meters of copper wire to get it red hot in free air initially , but of course after the reaction starts , the exotherm of the reaction will keep the catalyst plenty hot , and the power supply would only need to labor hard for a brief time to initiate the reaction .

[Edited on 2-11-2006 by Rosco Bodine]

gsd - 2-11-2006 at 10:13

Let me make it clear that I have not gone through this thread completely as it is fairly a long one; so kindly excuse me if I am repeating the posted matter.

While doing my engineering, I had done summer vacational training in an "ethanol to acetaldehyde - air oxidation" plant.

Ethanol vapours and air are premixed and immediately fed into a reactor which is a squat cylindrical vessel having vertical tubes on which several layers of gauze made from very pure silver metal are tightly wound. The vapour air mixture passes across this layer of catalyst. The reaction is exothermic and the bed temperature is maintained at 550 Deg C., by coolant circulation in the tubes. The contact time is very short ( < 0.1 sec), per pass conversion is about 48 % and yield about 85-90 %

The Interesting this about this reactor was the startup procedure. To this big reactor ( Diameter about 1.2 m, I don't recollect exactly) are attached 3 small pilot reactors of 200 mm dia and 300 mm length, at 120 Deg angle. These small reactors are packed completely with copper wire gauze and are heated with electrical resistance heaters packed within the copper wire gauze layers.

The same feed of ethanol + air mixture is passed thru' each of there reactors and the outcoming hot vapours from small reactors are directed onto the silver wire gauze of main reactor. These vapours slowly heat up the silver catalyst and after it is above 300 Deg C., Feed is stared to the main reactor and the pilot reactors are discontined.

gsd

Jdurg - 2-11-2006 at 10:25

I haven't had a chance to read through the entire thread and while it's been many years since I had biochemistry, would it not be possible to take some ground up beef liver (which should be fairly cheap) and use the alcohol dehydrogenase contained within to convert the ethanol to acetaldehyde? Or, as I'm guessing, is the yield so poor and the extraction so complex that it's really not worth it?

Rosco Bodine - 2-11-2006 at 10:29

I wonder what the catalytic heater element used on
those propane fueled portable camping and icefishing heaters would do if it was fed an ethanol vapor fuel
instead of propane ?

There may already even be such infrared heaters designed
to operate on denatured alcohol , and it could very well
be that acetaldehyde is an intermediate oxidation product ,
which could be made the principal product if the air supply
was restricted to prevent its further oxidation .

Mooooo......Mooooooo , Mooooooooo

Sorry , I couldn't resist

@ fractional
Have you taken a look at that Dony-Henault article
reporting a quantitative yield of acetaldehyde via
electrolysis at a specifically limited voltage of 1.3 to 1.66 ?
That was on a platinum anode , and I wonder what silver
would do .

Anybody got access to that reference ?

Dony-Henault

Ztschr. f. Elektrochemie 6 , 533 , ( 1900 )

[Edited on 2-11-2006 by Rosco Bodine]

S.C. Wack - 2-11-2006 at 16:02

Tried that when the sportcats came out a few years ago. Oddly enough I found those better at making formaldehyde (with MeOH obviously) than acetaldehyde, though my experiments were crude and so far just for hahas. Not being engineering-minded, I felt that experiments with it were best directed elsewhere.

Vapor indeed. Unless the feed of either air or vapor is dilute much of the alcohol will burn off due to the exothermic self-sustaining nature of the reaction and the small amount of heat necessary to get it going.

Rosco Bodine - 2-11-2006 at 16:51

What I was thinking is maybe put the catalytic burner head inside a sealed chamber with an observation port
and a thermometer , and control the air supply and the
alcohol vapor flow to the burner . Fire it up in a normal
heat producing mode where it is getting plenty of air
to burn the fuel all the way to CO2 , and then start
reducing the air until it is outputting CO , and then gradually reduce the air further until hopefully the
aldehyde is what is being produced . There may be
a niche condition of temperature and mixture where
the reaction would proceed pretty well at a stable rate
and produce lots of the desired aldehyde .

fractional - 3-11-2006 at 01:19

Rosco,
I also think that silver-plated wire is the way to go. It gives you the catalytic performance of silver at the price of copper wire (or just a bit more). The conductivity of the wire will not change much, but the emissivity will. I found a figure for the emissivity of silver plating of 0.06. For the previous example of a length of 2.85m of 0.5mm dia. wire siver-plating would yield a temperature of 1326 degC which is probably too high, even considering losses. A 0.6mm dia. wire, length 4.1m, brings you back to 1123 degC, which is probably more realistic.

All these calculations show that the emissivity is a crucial factor in the calculations and the published figures are often miles apart, so if one wants to put such a system in place one should perform a few dry-runs first, using a power source that can be regulated somewhat.

> @ fractional
> Have you taken a look at that Dony-Henault article
> reporting a quantitative yield of acetaldehyde via
> electrolysis at a specifically limited voltage of 1.3 to 1.66 ?
> That was on a platinum anode , and I wonder what silver
> would do .

> Anybody got access to that reference ?

> Dony-Henault

> Ztschr. f. Elektrochemie 6 , 533 , ( 1900 )

Yes, I did read it and I find it extremely interesting. A platinum electrode is one of those things one would like to have, isn't it? Electrochemistry is not my strong side (to put it mildly) so I don't know what the use of a different anode material would do, e.g. the effects of overvoltage, etc. I tried to find an article from 1899 also in the "Zeitschrift f. Elektrochemie" on the production of Chloral by electrolysis, but with no success so far.

What I can say is that if some good soul scans the article I will be more than happy to translate it and put it on the board.

not_important - 3-11-2006 at 01:22

SCW is right, once you get above a few hundred C and there is oxygen present then the reaction tends to go to full oxidation and thermal runaway. The industrial processes use a rather high speed flow of reactants to help avoid too much loss from that route, like NOx production from air - quickly heat and chill.

Another thing to remember is that the Cu/Ag route will produce aldehyde without any oxygen present, the added O2/air is used to remove hydrogen to force the reaction further to completion. Those catalytic burners are targeted at full oxidation of hydrocarbons, they may not function well for this more limited reaction.

Rosco Bodine - 3-11-2006 at 07:10

Some of the campstoves and lanterns which burn white gasoline use a pressurized tank for the liquid fuel which
is squirted under pressure through a very small orifice
into a larger bore tube which is heated by the burner ,
and the liquid spray is flash boiled to a vapor in that
" vapor generator tube " which preheats and vaporizes the liquid fuel on its path to the burner , scavenging heat from the final output for the preheating of the fuel .

The same principle and indeed the same fuel tank and
fuel generator tube , perhaps with a couple of added
sections in length .....might be directly applicable for
an ethanol vapor generator if the copper tube containing
the catalytic material was coiled around the generator
tube and then insulated around the outside with a sleeve
of kaowool or fiberglass . A thermocouple could be attached to monitor the temperature . The first few inches of the generator tube and the first three or four
coil loops of catalyst containing tubing could be left partly uncovered with insulation so it could be exposed to
external heating by a bunsen burner for initial heating
when firing up the apparatus . A Tee fitting and needle valve could be interposed between the fuel tank and the vapor generator tube , or perhaps at a third of the length of the catalyst containing tube , for admitting air as needed to speed the warmup of the apparatus by complete oxidation of the fuel initially , which should get the converter temperature high enough , that the oxidation could then be transitioned to the more anaerobic production of acetaldehyde by gradually reducing the airflow .

Supplemental electrical heating could be provided if needed by a cylindrical heating element , a " watt rod " along the
outside of the coil under the insulation , or a few of the coils could be wound around the heating element directly .

The idea of loading the catalyst inside a coil of copper tubing
is perhaps not the optimum arrangement , if a short contact
time with the catalyst is what is desired , a straight
section of larger tubing , or a concentric arangement of
inner vapor tube and an outer tube containing the catalyst
may serve better . A compact assembly the size of a soup can may have superior characteristics to something larger the size of a map case or blueprint tube .

Another arrangement of catalytic burner which may be applicable is similar to the vertical " fluidized bed " concept . A funnel shaped copper bell , like a large reducer adapter sleeve solder fitting at the large opening and threaded at the smaller bottom opening ,
could be filled with layered pieces of silver coated copper wire braid and chopped wire whiskers , and fed with ethanol vapor from the bottom through a copper tubing having two or three loops of the tubing wound around the outside
of the reducing adapter to provide preheating of the entering vapor . A grid of wires laced across the large opening could be used to keep the spongy wad of catalyst pieces secured inside the catalytic " burner " head . Something like this would provide a rapid transit and brief
contact time for the ethanol vapor . A length of straight
copper pipe could be added to the copper bell to increase
the depth of the catalyst bed if needed , until the optimum
reaction zone dimension for the particular apparatus was discovered by testing .

To simplify greatly this whole endeavor I think it would be best to first use a modification on the patents method .
The catalytic reactor section need not be made of quartz
nor should the wire material be made of pure silver if
my earlier guess is correct that silvered copper braid material
should work about as well . All that should really be required
is a straight four inch section of 3/4" copper tube stuffed with layers of the catalyst wire mesh and having its ends
fitted with 3/4" to 1/4" brass or stainless compression reducer couplings for the vapor inlet and exit . The catalyst section is compact enough to be preheated easily by a meker burner with a wing adapter flame spreader . The brass compression couplings on the ends of the catalyst chamber could be wrapped with fiberglass ribbon for insulation , and the bare 3" middle section heated by the burner . The smaller copper inlet line could be hairpin bent
( U-bend ) back across the coupling and spiraled around
the catalyst containing section for vapor preheating , a
smaller copper capillary tubing such as is used in refrigeration would be needed for this tight spiral preheater .
I believe I have seen this small copper capillary tubing used
as supply tubing to pilot lights on gas appliances , and I will
do some shopping and scrounging to see what can be found in the way of fittings for making a modest lab scale device .

The silvered copper braid is something which will have to ordered , but simply treating ordinary copper braid scavenged from coaxial cable with silver nitrate may be the better approach in keeping the experiment to over the counter materials .

For the vapor - air mixture control , the setup will be based
on a bubbler in ethanol and an aquarium pump as described earlier .

[Edited on 3-11-2006 by Rosco Bodine]

Eclectic - 3-11-2006 at 14:56

There is a knitted copper mesh material available from http://www.partyman.se and other alcohol oriented places that they sell for column packing. It's used industrially for scouring the crud from plastic injection molding machinery parts. Chore-Boy (used to be Chore-Girl brand) copper scrubbers are similar.

[Edited on 3-11-2006 by Eclectic]

Rosco Bodine - 3-11-2006 at 15:30

Yeah I think this sort of setup is entirely workable
and could be made into a suitcase sized apparatus .
If ~90% yield is gotten in a single pass through
a catalytic converter of compact size , that is
entirely efficient enough for a practical method
and source for acetaldehyde as an intermediate .

Thinking further on the design , any unreacted
ethanol vapor could be stripped from the output simply by bubbling through an airstone in warm water , the alcohol would enter the water , but the more volatile acetaldehyde would blow through , while it could
be cooled further in an empty glass jug in an ice bath ,
and then bubbled into cracked ice and water in a
cylinder cooled in an ice salt bath . I believe that this
" Two jug - one tall bottle " sort of arrangement and
using gas dispersion stones in the first and last ,
with a swirling flow in the second , would work better
for purifying and capturing the extremely volatile
product in frigid water solution , than would trying
to condense it in conventional condensers .

Acetaldehyde from PET ?!?!?!

Aqua_Fortis_100% - 20-1-2007 at 19:58

firstly sorry by ressussiting this old thread but when i searched some things about acetadehyde in portuguese , the google show me a special result :

Quote:

from this page :
O acetaldeído é subproduto da degradação do PET. Ele é formado quando a resina PET é submetida a altas temperaturas, normalmente utilizadas na fabricação e transformação da resina, onde o polímero é aquecido acima de sua temperatura de fusão.

A preocupação com a presença de acetaldeído nas embalagens de PET se deve à alteração de gosto que este pode causar no produto embalado.

something as :
" the acetaldehyde is a subproduct of the decomposition of PET. It is formed when the PET resin is submited high temperatures , usually used in resin manufacture and modification, where the polymer is heated above of their melting point.
The worry with the Acetaldehyde presence in PET containers is due the taste which this can cause in the wrapped products (foods) ."

^sorry, this is a poor english but is some compreensible (eh?) ^

anyone tried getting acetaldehyde from this "method"? what about???

Quote:

originally posted by vulture:
The main problem with the production of acetaldehyde from ethanol is that when you use water as a solvent, you're always wasting aldehyde by conversion to acetic acid.

I'm actually only interested in acetaldehyde due the pentaerythritol manufacture... if i try distill this directely in cooled CHOH (with some Ca(OH)₂) this will improve the yield of the CH₃CHO coleted? Because the acetaldehyde react with formaldehyde (before?) the conversion for acetic acid in contact whit water..(?????)
or maybe, try DRY destill in the receiving cooled flask, then adding this in calcium hydroxide/formaldehyde solution..
thanks and sorry for anything...

[Editado em 21-1-2007 por Aqua_Fortis_100%]

guy - 20-1-2007 at 21:40

Ethanol + copper acetate (or palladium) + Sodium acetate(base) ---heat---> Acetaldehyde??

Make sure there is no water or else it will convert to acetic acid.
============

Copper catalyzed alcohol oxidation to ketones and aldehydes

Abstract:
An efficient, copper-based catalyst has been discovered that oxidizes a wide range of
alcohols into aldehydes and ketones under mild conditions. This catalytic system utilizes
oxygen or air as the ultimate, stoichiometric oxidant, producing water as the only
by-product.

[Edited on 1/21/2007 by guy]

Aqua_Fortis_100% - 21-1-2007 at 05:50

guy ,this is a very nice pdf!!!

but i have a doubt : they discribes a catalyst made from CuCl ,phenanthroline(phen) , K2CO3 and some others substances @ 70 to 90°C...
about the CuCl: the oxigen in process oxodizes the copper in Cu II ? has this similar or same eficience as catalyst?
thanks

guy - 21-1-2007 at 13:51

This method is less complicated, provided you have pyridine and palladium acetate. Works with normal pressure. The reason it works with palladium is because it can make the alcohol do a beta-hydride elimination.

Attachment: palladium_catalyzed_alcohol_oxidation.pdf (62kB)
This file has been downloaded 280 times

Nerro - 21-1-2007 at 14:46

pyridinium chlorochromate is an oxidizer which should oxidize only to the CHO (rather than proceed to the COOH).

I've used it in a practical and it worked quite well.

Magpie - 24-1-2007 at 16:04

Oops. I thought this thread was "aldehyde synthesis." My apologies.

I have been oxidizing n-butanol to n-butyraldehyde using the classic and well known dichromate method:

3CH3(CH2)2CH2OH + Na2Cr2O7 +4H2SO4 --->
3CH3(CH2)2CHO +Na2SO4 +Cr2(SO4)3 + 7H2O

This reaction is a bit hard to control as it is exothermic. And one has to keep the pot hot enough so that the aldehyde will be immediately driven to the condenser before it has a chance to oxidize further to butyric acid. But you don't want the pot too hot or you will drive off too much water and butanol into the distillate. The apparatus I used is shown in the attached photo. As you can see the clear alcohol is being added via dropping funnel. Although I have not done final workup this procedure appears to have given me some nominal amount of aldehyde.

My procedure (Brewster, 1962) specifies something I don't understand. It calls for dichromate at a mole ratio to alcohol of 1:1 instead of the stoichiometric 1:3. The same text, however, in a 1977 edition, changes from n-butanol to n-propanol, and uses a stoichiometric ratio. It also reverses the dropping funnel reactant to dichromate/H2SO4/water, with the n-propanol in the pot. I tried this with the n-butannol and it was a complete failure (disaster), never getting hot enough to flash off the aldehyde and then giving me a runaway when 90% of the dichromate had been added.

So if you have any ideas about the mole ratios specified for this type of reaction I'd like to hear them.

[Edited on 25-1-2007 by Magpie]

n-butyraldehyde.jpg - 59kB

Rosco Bodine - 24-1-2007 at 17:23

Here's something that is relevant and perhaps directly
applicable to what you are doing , with the bonus of having
an easily regenerable reagent which reportedly has a good efficiency in both the oxidative reaction as well as the regeneration .

[Edited on 25-1-2007 by Rosco Bodine]

Attachment: US4297520 Aldehydes via Dichromate Oxidation with electrolysis regenerable reagent.pdf (326kB)
This file has been downloaded 326 times

bio2 - 24-1-2007 at 18:16

Magpie, that's an interesting looking heating mantle
you've got there.

Did you make it yourself with that metal ring looking
heater?

Magpie - 24-1-2007 at 19:34

bio2, that is just a regular Glas-Col 500 mL mantle sitting in an iron ring with fiberglass fabric support straps sewn onto it in an "X" pattern. These rings are specially made for that purpose in different sizes and are available through the scientific supply houses. I have a 500mL and a 100 mL size as these are my mantle sizes. With these mantles I can heat all of my RBF's from 25mL to 500mL.

chemrox - 27-1-2007 at 16:41

So given a way to make acetaldehyde.. it doesn't last very long unless you polymerize it to paraldehyde a substance with certain virtues of its own not the least of which include its use in certain biological test reagents .. so extending the discussion, does anyone have a facile method for taking acetaldehyde to paraldehyde? I tried one published on Erowid and it was bogue...

fractional - 28-1-2007 at 04:51

From Cohen, Practical Organic Chemistry, 1910:

" Add a drop or two of concentrated sulphuric acid to 1 c.c. of [acet]aldehyde. The mixture becomes hot in consequence of the aldehyde undergoing polymerisation to paraldehyde (C2H4O)3, b.p. 124deg, which separates as an oil on adding water."

The sulphuric acid serves as a catalyst here. This reaction can be used advantageously to transform acetaldehyde to paraldehyde immediately, rather than storing (or trying to store...) acetaldhyde. Acetaldehyde produced in whatever way is led into a suitably sized RBF with a few drops of sulphuric acid (typically "one drop per cc. of acetaldehyde"), yiedling paraldehyde.
The reverse reaction takes place when paraldehyde is heated again with a few drops of sulphuric acid. "Paraldehyde does not show the characteristic aldehyde reactions; on destillation with dilute sulphuric acid it is converted back to the ordinary variety" (Gattermann, Practical Methods of Organic Chemistry). The liberated acetaldehyde can be collected in a cold-trap (e.g. cooled with an ice/salt mixture, etc.).

[Edited on 28-1-2007 by fractional]

Rosco Bodine - 28-1-2007 at 08:22

Paraldehyde is physiologically active IIRC , it is a hypnotic similar in action to chloral hydrate . So you might wish to be careful with this material , so as not to nod out unexpectedly .....and I don't recall what was the route of exposure ....contact , inhalation , or ingestion ....but
it is not a benign material .

fractional - 29-1-2007 at 04:20

Rosco is absolutely right about paraldehyde: it is physiologically active and a controlled substance (at least here in Europe). One can avoid handling this substance by applying a minor modification to the procedure:

"If aldehyde is cooled and treated with sulphuric acid, or if at the ordinary temperature gaseous hydrochloric acid, sulphur dioxide, or other compounds are passed into it, a solid polymerisation product, metaldehyde, is formed; this can also be coverted back into the ordinary variety." (Gattermann).

As a solid, metaldehyde is easy to handle, but it is also toxic, especially by inhalation. Wikipedia claims that it used as camping fuel for small stoves. I don't know about this, though.

Magpie - 1-2-2007 at 17:09

This is a followup to my post on making n-butyraldehyde from n-butanol using dichromate. I made 3 batches. The 2nd two were an effort to improve the control or efficiency of the 1st. The 1st was "by the book," only 1/3 scale because of the smaller size of my 19/22 glassware.

I didn't bother to calculate yields from each batch but just combined them for a final distillation to isolate the aldehyde. Upon review I think the book procedure is the best. The 2nd batch where I added the oxidant instead of the alcohol was pretty much a failure/disaster/runaway. For the 3rd batch I tried to conserve oxidant by using 2/3's of the specified alcohol and 1/2 of the specified oxidant. Near the end of the alcohol addition I ran out of oxidant as was evident from a lack of reaction as the alcohol was dripping into the pot.

I ended up with about ten mLs of aldehyde as a distillate from a fractional distillation using a 4 inch (10 cm) column packed with broken glass. Instead of coming over at the specified boiling point range of 72-76C (bp = 76C) it came over at 66C. I believe that this likely is an azeotrope with water which is 90.3% aldehyde and has a bp = 68C. I don't know what else to think.

I ran some qualitative tests on this distillate. It gave a positive test for Tollen's reagent (silver mirror) but a negative test for Fehling's reagent (Cu2O ppt). It gave a positive test with 0.3% KMnO4. It produced a small amount of white crystals after mixing with a saturated solution of potassium metabisulfite and cooling.

In conclusion I feel that this is an interesting but touchy way to make an aldehyde, and that one shouldn't expect a high yield. I would be interested in hearing about anyone else's experiences with this method.

Edit: I also wanted to mention that my aldehyde had a smell reminiscent of squeezed orange peels. It was pungent and overwhelming if I smelled too much of it.

[Edited on 2-2-2007 by Magpie]

fractional - 3-2-2007 at 04:13

Butyraldehyde forms an azeotrope with water:

b.p. 68,0 degC, with 90.3% butyraldehyde and 9.7% H2O in the azeotrope. (My source, a table of azeotropes from an old edition of the HB of Chem and Physics, only says "butyraldehyde", so I can only assume that they mean n-butyraldehyde)

So this seems to explain the lower boiling point. However, the table also indicates that two phases should be formed (with 96.8% butyraldehyde and 3.2% H2O in the upper and 7.1% butyraldehyde and 92.9% H2O in the lower layer). Is this in line with your observations?

Magpie - 3-2-2007 at 10:19

@fractional: Interesting. No, I cannot see two phases. I am giving some thought to dewatering with 3A molecular sieves and then rechecking the boiling point.

Nicodem - 4-2-2007 at 13:15

Magpie, you might want to try out the method from the attached paper. It is ridiculously easy, but therefore also kind of suspicious (especially since it is from Tet. Letters and there is no experimental data). It would be nice if someone verify it and report back the results, since I might have a use for it on an aliphatic alcohol as well. n-Butanol is not one of the substrates tested, but the yield from n-pentanol to n-pentanal was 65% which sounds really good for an aliphatic alcohol.

PS: Molecular sieves on aliphatic aldehydes does not sound as a very good idea…

Attached is: Tetrahedron Letters, 43 (2002) 8843-8844. doi:10.1016/S0040-4039(02)02234-7

Attachment: Selective solvent-free oxidation of alcohols with K2Cr2O7.djv (170kB)
This file has been downloaded 304 times

Magpie - 4-2-2007 at 15:56

@Nicodem: Thanks for that reference. It seems like a simple method for making aldehydes and I might give it a try.

Why do you say not to use molecular sieves to dry an aliphatic aldehyde?

not_important - 5-2-2007 at 00:57

Quote:

Originally posted by Magpie
Why do you say not to use molecular sieves to dry an aliphatic aldehyde?

The sieves can function as bases or acids, depending, and give condensation and/or cross-redox products.

Sodium sulfate for a first drying, polish with MgSO4.

leu - 19-3-2007 at 13:37

Butyraldehyde is synthesized from butanol using manganese dioxide using a column in Proceedings of the Chemical Society 110 (1964)

[Edited on 20-3-2007 by leu]

Attachment: harrison.zip (20kB)
This file has been downloaded 265 times

more interesting info about V2O5:H2O2

Rosco Bodine - 21-12-2007 at 04:00

This should have many possible uses .

Attachment: Synthesis of Vanadium Oxide Gels from Peroxovanadic Acid Solutions A 51V NMR Study.pdf (119kB)
This file has been downloaded 178 times

Siddy - 23-12-2007 at 21:17

^ I cant work that link?

What about thought Ethyl Chloride (Chloroethane)?

EtOH + HCl > EtCl
(ZnCl2 catalyst)

EtCl + H2O2 > EtO
(catalyst?)

carbonic - 22-2-2008 at 15:03

I have a paraldehyde synth that's up for discussion or debunking. I was not trying to make paraldehyde, just to test some oxidizers so I wasn't taking notes or anything but it's easy to repeat if someone would like to check it against a Tollin's test or something.

I used two routes, percarbonate alone and percarbonate with ferric chloride. It seemed to me that percarbonate was a nice way to get a gently basic H2O2 oxider so I used ethanol as a test platform. H2O2 solution plus iron is called Fenton's reagent and is commonly used to oxidize contaminants all the way to carbon dioxide. It seems the ferrous (not ferric) ion busts the H2O2 into hydroxyl radicals, which are vicious oxidizers. From my tests, the ferric chloride just precipitates iron which makes all the H2O2 fizz out of solution. So although I got similar results using each method, I doubt the ferric was helping.

At any rate, the synth was simple: Add oxiclean (basically pure percarbonate with some borate stabilizers) to vodka and heat. About a scoop of percarbonate to 100ml 50% EtoH was what I used but I did not try to optimize. After heating for about 10 minutes, what I found was upon cooling, the solution split into two layers. One test was to pipette some of the lower layer into a test tube run under cold water - it solidified. Run under hot water it melted again, and would be kind of sludgy if left at room temp.

The second test was to filter the whole shebang (to get out the insoluble carbonates) and drop in an ice cube and stick it in the fridge. Almost the whole hundred ml turned to sludge which was then filtered and subjected to the same melting/freezing tests.

At first I was a bit puzzled, as I had expected acetaldehyde as a water-soluble product, but then it occurred to me that peroxide was a very efficient polymerization initiator so the acetaldehyde was probably polymerizing as soon as it was formed, creating a less-soluble product that eventually dropped out of solution. The data on peraldehyde seemed to match the liquid that I had, so I called it a day and dumped it out.

Well that's it: oxiclean as an oxidizer, who knew? I may try again soon to see if the mystery liquid haloforms, but I think Tollen's would be a better test. I might get some useful data from haloforming it, because ethanol gives a really weak haloform, whereas real ketones/aldehydes haloform almost violently.

My results are easy to duplicate, so if anyone out there has the capability to better analyze this product, please let us all know!

Edited to add another question: Why the hell would anyone want paraldehyde or acetaldehyde anyway? What's it good for?

[Edited on 22-2-2008 by carbonic]

Filemon - 24-2-2008 at 13:54

I read in Organic Sintheses, it may reduce to aldehyde from carboxilyc acid with formic acid. Making the pyrolysis of the calcic double salt. I have looked for the reference but I don't find it.

Nicodem - 24-2-2008 at 23:06

You forgot to look for those references on this forum as well:
https://sciencemadness.org/talk/viewthread.php?tid=2223&page=8#pid80...

carbonic - 25-2-2008 at 09:48

but really, what is acetaldehyde good for?

Sobrero - 26-2-2008 at 05:08

Pentaerythritol synthesis

JohnWW - 26-2-2008 at 13:19

Yes, pentaerythritol, C(CH2OH)4, is made by the reaction of CH3CHO and CH2O in the presence of a strong alkali like KOH. The stuff is used for the manufacture of powerful nitro-explosives, especially the tetranitrate ester.

[Edited on 27-2-08 by JohnWW]

PHILOU Zrealone - 27-2-2008 at 03:34

Quote:

Originally posted by carbonic
but really, what is acetaldehyde good for?

Reactive molecule to introduce CH3-CHOH- or CH3-CH= moiety into a bunch of molecules displaying affinity for the carbonyl part.

[Edited on 27-2-2008 by PHILOU Zrealone]

Filemon - 11-3-2008 at 17:04

Quote:

Originally posted by solo
Note : here is a recent posting on the subject at the Hive,.......".Novel Discussions"

slothrop
(Newbee)
12-17-02 10:58
No 390260
Benzyl alcohols to Benzaldehydes

From Synlett 2002, 12, pp2041-42,
A Novel and Efficient Oxidation of Benzyl Alcohols to Benzaldehydes with DMSO Catalyzed by Acids
Typical procedure: A mixture of 557 mg of benzyl alcohol, 0.15 mL of HBr (48 %) and 5 mL of DMSO was stirred in an oil bath at 100°C. TLC (petroleum ether/diethyl ether, 1:1) was used to indicate the completion of the reaction (3 h). To the reaction mixture were added 5 mL brine followed by extraction with 30 mL of diethyl ether. The ether layer was washed with brine (5 mL x 4). Evaporation of the ether and subsequent buld to buld distillation produced 530 mg of benzaldehyde in 95 % yield.
//Tyrone Slothrop

How does it work?

MagicJigPipe - 11-3-2008 at 17:20

This sounds almost too good to be true. Has anyone even heard of this before? Or tried it?

I suppose I'll try it tomorrow since I have all of those reagents.

PHILOU Zrealone - 12-3-2008 at 02:26

Quote:

Originally posted by MagicJigPipe
This sounds almost too good to be true. Has anyone even heard of this before? Or tried it?

I suppose I'll try it tomorrow since I have all of those reagents.

CH3-SO2-CH3 is maybe a mild enough oxydiser...I suspect it must turn into CH3-SO-CH3 and maybe into CH3-S-CH3...but then you will notice by the very distinctive smell of it

Nicodem - 12-3-2008 at 03:39

It is some kind of a variation on the Swern oxidation, but it can only work on benzyl alcohols. Alcohols having alpha-hydrogens succumb to side reaction under such harsh conditions. Instead they require acid scavengers and acid chlorides or anhydrides for the DMSO activation under <0°C temperatures.

PS: DMSO is not Me-SO2-Me, it is Me-SO-Me and after reduction with benzyl alcohol (or whatever else) it converts to dimethyl sulfide (Me2S).

detritus - 28-4-2008 at 18:30

In the dictonary of applied chemistry on google books, p103 second column the dichromate + sulfuric oxidation is mentioned, but also another another I thought was good.

Manganese dioxide - aka the black packed substance in an alkaline battery. If you cut open the bottom of a big battery like a D cell, you can scoop out the zinc powder anode and save it. Watch out, it is caustic (er, alkaline).

Then, bend the case a bit to crack apart the 50+g of MnO2. I put a few g of this MnO2 plus a g or so of bisulfate beads into a jar and added everclear. Not much happening instantaneously, but when left overnight I saw a "dew" of droplets had appeared at the top of the walls. Opening and smelling, it was undoubtedly the light, clear fruity scent of acetaldehyde.

I suppose that conc. H2SO4 is better suited for this than the weaker bisulfate salt, but at least it proves that the cheap and readily available MnO2 can oxidize a primary alcohol to an aldehyde.

Formatik - 29-4-2008 at 16:44

Quote:

Originally posted by detritus
In the dictonary of applied chemistry on google books, p103 second column the dichromate + sulfuric oxidation is mentioned, but also another another I thought was good.

Manganese dioxide - aka the black packed substance in an alkaline battery. If you cut open the bottom of a big battery like a D cell, you can scoop out the zinc powder anode and save it. Watch out, it is caustic (er, alkaline).

Then, bend the case a bit to crack apart the 50+g of MnO2. I put a few g of this MnO2 plus a g or so of bisulfate beads into a jar and added everclear. Not much happening instantaneously, but when left overnight I saw a "dew" of droplets had appeared at the top of the walls. Opening and smelling, it was undoubtedly the light, clear fruity scent of acetaldehyde.

I suppose that conc. H2SO4 is better suited for this than the weaker bisulfate salt, but at least it proves that the cheap and readily available MnO2 can oxidize a primary alcohol to an aldehyde.

That MnO2 is also mixed in with carbon, so be careful using that in any experiments, e.g. as a catalyst in the thermal decompsition of KClO3 to generate oxygen gas.

detritus - 30-4-2008 at 15:28

good point. do you happen to know the approxamate ratios used in alkaline cells? Carbon to MnO2, that is...

Formatik - 2-5-2008 at 01:07

Quote:

Originally posted by detritus
good point. do you happen to know the approxamate ratios used in alkaline cells? Carbon to MnO2, that is...

I'm not sure exactly. I think there might be a patented formulation for the certain battery types. Will have to look into it more later.

Extraction of the pure compound would be some hard work. Some ideas of extraction: Any water solubles like the chloride could be removed by heating the solid with water and strong stirring. The carbon is insoluble in water but so is MnO2, though MnO2 will dissolve in HCl (Caution: chlorine gas): MnO2 + 4 HCl -> Cl2 + MnCl2 (pink) + 2 H2O. The carbon should be insoluble. Should be able to get MnCO3 (insoluble) from MnCl2 and Na2CO3 solutions. Then heat MnCO3 to 260°C (in air), and react the residue with very dilute cold HCl acid to get MnO2. It is also said to form by precipitating from MnCl2 with an alkaline hypochlorite solution, etc.

[Edited on 2-5-2008 by Schockwave]

Jimmymajesty - 9-7-2009 at 10:48

Sorry for bringing up an old tread.

I once made peroxi-acetone in my old kewl days. I didn't read forums like this at that time, so I thought that the warmer the solution the more peroxi-acetone will form

, so I mixed acetone with hydrogen peroxide, I can't remember the ratios (I also didn't care too much with it

) but I seem to remember that the acetone were in large excess.

I dumped the HCl into the mix by mililiters until it got warmed then put it into my cellar, after a couple of days filtered off the product...

The interesting point is... when i took the remained most-wit-buddha-knows-what-in-there solution, heated up a copper wire and put in it and it started to foam and heat immeadiately, I never had acetaldehyde only did tube experiments with hot penny, but the smell was the same IIRC, the whole solution (about 300ml) were boiled out of the jar, a lot of gas were generated!

Does somebody has a guess what could that be?

Any answer or guesswork would be appreaciated. Thanks!

DJF90 - 2-9-2009 at 14:59

Seeing as the thread is "alive" again I'll add something.

@Nicodem: This is the Kornblum oxidation. The HBr is there to form the alkyl bromide, which is attacked Sn2 style to form the same activated complex as all the other related DMSO oxidations (pfitzner moffatt, swern, onodera-albright, albright-goldman etc etc.) The reaction is NOT limited to benzyl alcohols. The original work was done with alpha-haloketones to yeild glyoxals, but some modifications were introduced to make it work better for other substrates. In fact the benzyl halides reacted to give poor yields of benzaldehyde. Generally the conditions consist of an alkyl halide, NaHCO3 as a base, and DMSO as solvent, temperature ca. 140C. If X= Cl or Br, then 1.5eq. NaI can be added to facilitate reaction. The reaction generally works better with the corresponding tosylates (X= OTs) and this will work with primary substrates to give the corresponding aldehyde. The tosylate can be prepared as "normal" using TsCl on the appropriate alcohol, or by using silver tosylate (TsOAg) on the corresponding halide. The tosylate is then reacted with DMSO, and the conditions are somewhat milder if I remember correctly; Stirring the tosylate in DMSO at room temperature is sometimes satisfactory.

Jimmymajesty - 3-9-2009 at 11:39

I made acetaldehyde by refluxing 93% ethanol on hot copper, after 4 hour of refluxing the acetaldehyde started to distill over the column... I think it was heavily contaminated but sniffing it behaved the same way as formaline.
Theres nothing in the first couple of seconds then you cry like hell...

I also pured a small amount of destillate (I do not know what was the contaminant but the boiling point of the distillate was much higher than 20°C) into saturated NH3 solution and it warmed a lot and gave a white emulsion (I think it would have been impossible to filter) anyway my three necked flask broken at the 5th hour. So I shut down the setup... When I went back to check the setup the whole thing burned... scared the shit out of me to put it soft...

I ordered another flask for my home-made acetaldehyde plant and I will give this another try when I have the time and post the results.

By the way I can post picture of the whole setup taken before it fell apart if anyone is interested.

Picric-A - 3-9-2009 at 12:01

Can NaHSO4 be substituted for KHSO4 in the dehydration of tartaric acid to pyvuric acid?

Klute - 3-9-2009 at 14:04

Please, do post theses pictures!

Pictures from the setup

Jimmymajesty - 5-9-2009 at 08:15

The first picture is talking to itself... the tube were filled with copper foil peeled off from gauging rods

The second is destined to illustrate the small tube in the three necked RB flask. It is necessary for the continuous reflux of ethanol.

The setup is on the third picture...

The condensation front in the condenser was kept at the level of the second bubble IIRC.

I inserted two scrubbers opposed to each other to the end of the plastic tube so as to the starting point of the oxidation would be indicated, when the reaction started I sampled the generated gas once in a while in a test tube, smelled and lit it... it seemed to mainly consist of hydrogen because it was odourless and burned with a blue flame in dark.

I am gona buy a controller for the next run too to keep the reactor temperature below 300°C.

I saved the milk like product, which I think mainly consists of aldehydeammonia... I do not know what to do with it in this form... any idea?

Klute - 5-9-2009 at 17:32

Beautifull setup! Unfortunate that the experiment wasn't very conclusive.. Please let us know of futur tries!

Jimmymajesty - 11-10-2009 at 04:38

Ok... everithing gone to waste what I wrote abot half an hour, this is definitely not my day.

So, I gradually increased the setpoint of the glass reactor from 280°C to 420°C.

From two liter ethanol after a couple of hours of run, I fractionated about 50ml foul smelling liquid T=20-60°C wich gave cristallyne solid on addition of NaHSO3.

I am gona try again with copper foil.

Because... I used stripped copper cord stuffed in the glass tube at this experiment.

[Edited on 11-10-2009 by Jimmymajesty]

Da_Boss - 13-10-2009 at 01:36

Could you make acetaldehyde from chloral hydrate?

DJF90 - 13-10-2009 at 05:48

Not likely, unless you want to spend a long time/expensive reagents removing them chlorine atoms...

Aqua-regia1 - 23-11-2009 at 11:32

Reply Post: 2312 ethylene glycol - again

Has anybody acces to this paper:
Tetrahedron Volume 58, Issue 11, 11 March 2002, Pages 2091-2094 Ethylene glycol to acetaldehyde-dehydration or a concerted mechanism

Sedit - 23-11-2009 at 11:44

Since this is not the place for it you may have better luck in the Reference request thread then you will here.

bbartlog - 7-12-2009 at 18:51

Looking back through this thread, I see that ethylene glycol has been discussed in the context of sulfuric acid oxidation, but not otherwise (and it looks like dioxane is actually what you'll get...).
However, after seeing this: http://www.sciencemadness.org/talk/files.php?pid=75149&aid=1734 elsewhere here, I wonder about hypochlorite as a way of oxidizing ethylene glycol to acetaldehyde.

In this case, it looks like the primary products are formaldehyde, acetaldehyde and ethylene. But they're discussing an uncontrolled oxidation with concentrated oxidizer. It seems like slow addition of hypochlorite solution to hot ethylene glycol, with condensation of any evolved gas, might result in a greater proportion of acetaldehyde.

I'll try this and report on the results.

So far as dioxane (or the possibility of other products) is concerned, it seems like the production of such a compound might be heavily influenced by the amount of water present in the system. It looks like condensation to dioxane would be driven by the water-withdrawing nature of H2SO4, so that some difference in conditions (like more water in the system) might instead allow the H2SO4 to act as oxidizer, and result in different products.

not_important - 7-12-2009 at 22:23

First, they are referring to polyethyleneglycol, H(-OCH2CH2O-)nH, not ethylene glycol.

Second, this is not a simple oxidation, the paper explicitly mentions radical mechanisms, look on page #5 of the PDF. I suggest that you might show how oxidation of HOCH2CH2OH (C2H6O2) leads to CH3CHO (C2H4O)

Third, attempting to keep it controlled looks as if doing so may be difficult; there are plenty of easier and higher yielding ways.

Nicodem - 8-12-2009 at 02:07

Bbartlog, ethylene glycol and acetaldehyde are in the same oxidation state. Therefore, you can not obtain acetaldehyde from ethylene glycol oxidation. I suggest you to learn how to count oxidation states as this is pretty much basic chemistry without which you can not do.

You can not just rearrange ethylene glycol or 1,4-dioxane to acetaldehyde using protic acids because primary alcohols do not undergo eliminations that easily, while the conditions required would be too harsh for the acetaldehyde to "survive". It might be possible by passing ethylene glycol or 1,4-dioxane vapors over some some solid acid (alumina, acidic zeolites, silica, etc.) at high temperature (300°C or more). Such heterogenous conditions should prevent the acetaldehyde to decompose, but still yielding a mixture of products. But this is not easily done in an amateur setting and besides I was not able to find any references confirming such an idea would work.

Aqua-regia1 - 8-12-2009 at 12:59

The pinacol rearragement of ethylen glycol doesn't work. I tested it, with several H2SO4 conc. The only one way: dehydratation route. (to difficult in home lab, therefore expensiv too) But dehydratation is not to very same oxidation.

bbartlog - 8-12-2009 at 13:34

I see what you mean about the oxidation states, C2H6O2 versus C2H4O. This is in line with what not_important says about the polyethylene glycol, not ethylene glycol, being the substance oxidized.

Quote:

I suggest that you might show how oxidation of HOCH2CH2OH (C2H6O2) leads to CH3CHO (C2H4O)

Looks like it can't. Oxidative glycolic cleavage might still be possible, leading to formaldehyde? Anyway, there is a reaction, but I have yet to distill the solution to try to separate the product(s). An interesting parallel between the Ca(OCl)2 / polyethyene glycol reaction and the one I observed (6% NaOCl + ethylene glycol) is that both seem to be delayed. They describe a 30 second delay before a fairly sudden hissing and fireball, while in the case of my mixture nearly five minutes (with shaking of the test tube) passed before the solution rapidly heated up. Could be purely thermal runaway, I might try a test tube in a beaker of ice water and see what happens. If it still heats suddenly after a similar delay then something else is going on.

Jimmymajesty - 24-3-2010 at 14:24

At the production of dioxane small amount of acetal forms which on hydrolysis releases acetladehyde but the acetladehyde reacts with alcohols (glycol in this case) to form acetals (I think).

It may wort to try to warm ethanol and drip NaOCl solution into it, here the product would be croton aldehyde which can also be used to make stuff

The home performed dehydrogenation is actually feasible, read the attached paper (oxidative dehydrogenation), it is not that difficult to make similar apparatus at home.

I collected some info on the web regarding acetaldehyde synth by dehydrogenation which I want to share with you not only for informational purposes!

I hope some of you will try out and improve the method, and finally post the results.

+Catalytic dehydrogentation is a better method to make acetaldehyde due to less side reactions. The copper catalysts perform better than type of silver and lasts longer.

+Cu-Co-Cr2O3 @ 280-350°C is used industrially (5w%Cobalt+2w%Chrome+93w%Copper), the method of cat. prep. consists of coprecipitation from acetate salts, and calcining at 550°C max. Then one have to reduce the cat. by hydrogen... I think it is not necessary as the cat. will be reduced under ethyl alcohol wapors anyway.

+The Cu to Cr mole ratio is optimal at 10:1.

+The yield is affected by the water content of the original water+alcohol mixture the more the alcohol the more ethyl acetate will form.

+Copper from electroplating seemingly do not catalyse dehydrogenation, high surface are is required! (When I read this I stopped electroplating copper to steel sponge

)

I also have the suspicion that the converter (catalyst used to oxidize stull like NxOy and CH into water etc. may be used to make acetladehyde in a controlled manner.

Attachment: Acetaldehyde production experimental.pdf (179kB)
This file has been downloaded 70 times

Melgar - 29-3-2010 at 06:10

I actually made some of this stuff recently. I took a piece of copper pipe and dissolved it in aqua regia. Then I neutralized with a base. You can use any base, but you can burn away the ammonia salts if you use ammonia, to get a purer CuO. The catalyst works even if sodium salts are present though. Anyway, once you neutralize, then boil away all the water, and the mixture will turn black. That's CuO, with other salts mixed in. If you neutralized with ammonia, the mixture will smoke and burn at points as the ammonium nitrate decomposes or oxidizes other components of the mixture.

The next step was putting the CuO into a big test tube. Then I got a two-hole stopper and ran a stainless steel tube to the bottom of the tube, then ran another one from the top of the tube to a beaker of cold water. I'm sure glass or copper tubes would work fine too, I just happened to have SS on hand. I boiled alcohol in a bottle connected to the inlet tube, then put an alcohol lamp underneath the test tube of CuO. As vapors entered the test tube, I could see patches of black CuO turning into pink patches of copper metal. The acetaldehyde vapors smelled like a fruitier, not-as-nasty version of formaldehyde. As in, it smelled a little like formaldehyde, but didn't burn my eyes and throat.

I realize I didn't control the temperature of the catalyst and thus probably generated some formaldehyde in addition to acetaldehyde, in which case the fruity smell was probably the acetaldehyde. It did work, although I have to add that this stuff has too low of a boiling point to be able to condense it efficiently or have it around in a pure state. You pretty much have to dissolve it in a liquid.

Melgar - 31-3-2010 at 14:49

Just discovered two more ways of making acetaldehyde. First is reduction of acetonitrile with tin(II) chloride in hydrochloric acid. This turns tin(II) chloride to tin(IV) chloride and acetonitrile to an iminium salt which is hydrolyzed to acetaldehyde. Look up the "Stephen aldehyde synthesis" for this one.

The other method is the ozonolysis of propylene. Those yellow torch tanks you find at the hardware store are mostly propylene, and you can CAREFULLY!!! bubble them into a polar solvent (preferably a nonflammable one) to dissolve it, then bubble ozone in to split it into acetaldehyde and formaldehyde. You need to do it in a reducing environment to get these products though. Also, the gas from these tanks typically has an odorant added to it, which will give it that sulfury gas smell, but that is at a really low concentration and shouldn't affect the chemical properties, although it would make it harder to tell by smell what your products are.

Fleaker - 31-3-2010 at 16:20

The sulfury gas smell would be rendered odourless by ozone! Not that my idea of fun is making ozone and using it as an oxidiser!

Interesting on the stannous chloride side. Please post more information/mechanism and references. I love my tube furnace reactions, but this method sounds VERY intriguing.

Melgar - 31-3-2010 at 23:47

Quote: Originally posted by Fleaker

The sulfury gas smell would be rendered odourless by ozone! Not that my idea of fun is making ozone and using it as an oxidiser!

You're right, although the gas is detectable even at really low concentrations so you'd probably still smell it if you didn't get it all. I have an ozone generator that I use to deodorize/sanitize stuff on occasion so I've already got that covered. On the bright side, the odorants tend to be methyl/ethyl sulfides, which are used as reducing agents in ozonolysis anyway.

Quote:

Interesting on the stannous chloride side. Please post more information/mechanism and references. I love my tube furnace reactions, but this method sounds VERY intriguing.

Apparently it requires tin(II) chloride dissolved in ether, then saturated with hydrogen chloride. Check out the attachment.

Yet another synthesis appears to be the destructive distillation of calcium formate and calcium acetate, which would also produce low yields and a lot of acetone, CO2, and hydrogen, but at least it's really straightforward.

Attachment: stephen aldehyde synthesis.pdf (254kB)
This file has been downloaded 33 times

[Edited on 4/1/10 by Melgar]

Melgar - 31-3-2010 at 23:56

Also, tin is pretty easily obtained from lead-free solder, since I have yet to see a lead-free solder that is less than 95% tin. However, the hardware store muriatic acid I have has quite a bit of iron dissolved in it, (visible by the yellow color) and this immediately plated onto the tin solder and seemed to prevent it from dissolving very much. Still, this seems to be a good way to get the iron out of my muriatic acid, if nothing else.

Jimmymajesty - 1-4-2010 at 00:04

Nice try! But I am afraid you only made small amount of the required stuff

I am going to co-precipitate cobalt and copper hydroxydes, pour the slurry to MgO, activated carbon, or alumina, and heat it to 500°C for some hours. Another way would be the one suggested by Melgar, that is to dissolve the hydrohydes in aq. ammonia, pour the solution to something porous and inert, vacuum treat the stuff then heat it then crush it in a mortar to granules. I can see one problem with MgO carrier, namely it absorbs water so when alcohol wapor is passed ower it it would become a gel and loose catalytic properties, so my preferred mat. would be activated carbon particles, they have a lot of surface and can not be dissolved in alcohol ofc. Or rather! the insulation from kanthal heating filaments, they are made of 96w% Al2O3, being totally heat and corrosion resistant.

Acetonitrile method? I also know some exotic procedure during which acetaldehyde is liberated, some diazotization e.g. but i dunno if you could make decent quantity of acetaldehyde by that..

Propylene ozonolysis in home lab?

I can only see countless problems. e.g. generation of ozone in useful quantities is a PITA. BTW the smell is probably from ethyl mercaptan which is oxidized by ozone to SO2 then SO3 if you use excess of ozone, I also have a suspicion that sulfur containing material are more prone to oxidation that propylene, also IIRC propylene+ozone=explosion unless low temps are used.

I am goint to try out the above posted catalysts asap and post the results.. that means months unfortunately.

Oh! When I made acetaldehyde with my previous setup by catalytic dehydrogenation, the smell was rather unpleasant and spicy when you took a nosefull of it, it means that a lot of side reaction occurred?!.. The themp of the condenser was not controlled, and the temp. control in the reaction zone was crude too.. I have to overcome these problems!

Melgar - 1-4-2010 at 01:12

My ozone generator can do 600 mg an hour in air, meaning it can make a little less acetaldehyde than that. The formaldehyde is a bonus if you can use it. Since it uses a 1/3 duty cycle on its highest setting, that's like a gram and a half overnight. Also, in an insulated container with lots of ice and calcium chloride, chances of explosions are minimal if your solvent isn't flammable. CH2Cl2 is used a lot for this reason, although I personally have yet to try it. Still looking for a decent reducing agent. Also, I'm pretty sure ozone attacks double bonds preferentially, then sulfur compounds after that. Oh, and mercaptans are oxidized to different things depending on the oxidizer, but rarely to SO2 or SO3.

Actually, the acetonitrile method seems like it would be the most likely to give good, consistent yields, since the iminium salt precipitates out and can be filtered from the ether. I'll probably try the destructive distillation route too since I have the formic acid, acetic acid, calcium chloride, and sodium hydroxide that are required.

Activated carbon will burn if there's oxygen present and it's hot enough, so there's a good chance it could reduce your copper oxide to copper metal and leave as CO2. Aluminum oxide is available as sandblasting grit, and that seems to be a good catalyst substrate. It's used a lot in industry anyway. Plus it's white, so you'd be able to distinguish your catalyst from the substrate if nothing else. Even silica (sand) seems like it could do the job well enough.

hissingnoise - 1-4-2010 at 04:36

Quote:

Actually, the acetonitrile method seems like it would be the most likely to give good, consistent yields, since the iminium salt precipitates out and can be filtered from the ether. I'll probably try the destructive distillation route too since I have the formic acid, acetic acid, calcium chloride, and sodium hydroxide that are required.

Hydration of acetylene seems simpler, requiring only C2H2, H2SO4 and Hg.

Jimmymajesty - 1-4-2010 at 05:34

A gram and a half overnight is not that much unfortunately.. but try it and post the results please! I am working in an olefin plant so pure propylene is not that hard to get

My ozone generator are made of a test tube with Al foil wrapped around it and a tiny wire in it, I drive the generator with a flyback transformer from an old television... without the current rectifier part. But a germicide lamp would also do the job.

I dont have such things like DCM or acetonitrile, and based on a quick search, acetonitrile is not that easy to make at home..

I would prefer dehydrogenation rather than catalytic oxidation, but if I were to apply catalytic oxidation as a last resort. I would make silver mirror to a glass tube then stuff the tube with silver sponge made of fusing AgCl and Na2CO3. To cut it short I try the activated carbon first (large surface area) then Al2O3 insulation rings.

The idea which was discussed upthread is more feasible than the formiate etc methods. Namely you melt tartaric acid with KHSO4 to get pyruvic acid, and that readily decomposes to acetaldehyde however I am not sure about the conditions and temps that the last part requires. The first part of the synth: tartaric+KHSO4 is on org synth webpage. BTW the tartaric acid is more OTC here than sodium hydroxide that is a big plus!

Lambda-Eyde - 1-4-2010 at 07:59

Quote: Originally posted by Melgar

However, the hardware store muriatic acid I have has quite a bit of iron dissolved in it, (visible by the yellow color) and this immediately plated onto the tin solder and seemed to prevent it from dissolving very much. Still, this seems to be a good way to get the iron out of my muriatic acid, if nothing else.

Let me see if I got this right - you just leave a piece of soldering tin in the hydrochloric acid, and the yellow color dissappears? I'm not pleased with the coloring of my acid, and I don't have reagent grade at the moment.

Some tin will dissolve anyways, so I think distillation of 20% HCl would be the best way to go if I want it somewhat metal-free.

Melgar - 1-4-2010 at 14:03

Well, I tried putting some solder in my HCl again today, and the iron didn't come out as quickly as I thought it would, although it did come out eventually. I think the yellow iron chloride just gets replaced by colorless tin chloride. I'm not sure how much success would come from distilling HCl, since it's a gas dissolved in water. My plan was to combine CaCl2 and H2SO4 to form HCl gas, then bubble that into distilled water. Unfortunately, that reaction got a little out of hand and sulfuric acid got spilled all over the place. I'll try that again with more precautions once my workbench is de-acidified.

To make acetaldehyde via destructive distillation you need hydrated lime, formic acid, and acetic acid. Hydrated lime is dirt cheap at the hardware store but you can make it from NaOH and CaCl2 if you just need a little and don't feel like making a special trip. The reaction seems as though it would produce CO2, formaldehyde, acetone, and acetaldehyde. Probably more acetaldehyde than anything else, although I hear destructive distillation yields suck anyway.

Melgar - 1-4-2010 at 14:23

Quote: Originally posted by Jimmymajesty

I dont have such things like DCM or acetonitrile, and based on a quick search, acetonitrile is not that easy to make at home..

DCM is actually really easy to get. Just go to the solvent section of your local hardware store (our favorite section!) and find the paint strippers. They all have warning labels on them saying "CAUTION, FLAMMABLE!", "CAUTION, POISON!" or both. Look for the ones that don't say "flammable". Since DCM is practically the only nonflammable solvent in this aisle, any paint stripper that doesn't seem to be flammable is probably mostly DCM. Also, look for the sprayable stuff, as in, the stuff that doesn't come as a gooey paste. It's a lot easier to distill.

Acetonitrile isn't that cheap at $50 a liter or so, but every so often a reaction calls for it as a solvent, so I have a bottle on hand. Supposedly, a recent shortage drove prices up and they aren't normally that high.

DJF90 - 1-4-2010 at 14:32

Paint stripper is generally (at least in the UK) a blend of dichloromethane and methanol, so should still bear the "flammable" warning... you'll just have to read the label (this applies to wherever you are; theres nothing worse than buying something, attempting extraction and finding the desired material is not a component).

Lambda-Eyde - 1-4-2010 at 14:37

Quote: Originally posted by Melgar

Well, I tried putting some solder in my HCl again today, and the iron didn't come out as quickly as I thought it would, although it did come out eventually. I think the yellow iron chloride just gets replaced by colorless tin chloride. I'm not sure how much success would come from distilling HCl, since it's a gas dissolved in water.

I have distilled HCl with success, but it's only the 20,2 % azeotrope that comes over. That is, theoretically, as I haven't quantitatively measured it.
The 30 % acid first fumes like crazy until it reaches the azeotropic point, when it starts to distill over. Interestingly, the azeotropic concentration has a much higher vapor pressure than the 30 % concentation - Just like the distillate I obtained. I don't like the idea of using precious (at least precious to me) H₂SO₄ to make HCl. There is an alternative way which involves using CaCl₂ as a drying agent to extract the water from aqueous HCl, making gaseous HCl.

Bubbling HCl gas made with this method through the distilled 20 % acid is a much more attractive method for me than using sulfuric acid. Alternatively I can wait a while and buy a liter from Chiron or Fisher Scientific...

But hey, this is going very off-topic. Sorry!

JohnWW - 1-4-2010 at 14:47

Paint stripper containing CH2Cl2 poses a hazard well beyond the fact that it is inflammable. When it burns, the major product would be phosgene, COCl2, which is deadly poisonous, and which was used, along with "mustard gas", by the Germans in WW1. Besides, volatile chlorocarbons are also known as liver toxins, if ingested or inhaled in any large quantity.

manimal - 1-4-2010 at 16:06

Quote: Originally posted by Melgar

Just discovered two more ways of making acetaldehyde. First is reduction of acetonitrile with tin(II) chloride in hydrochloric acid. This turns tin(II) chloride to tin(IV) chloride and acetonitrile to an iminium salt which is hydrolyzed to acetaldehyde. Look up the "Stephen aldehyde synthesis" for this one.

I'm pretty sure the Stephen aldehyde synthesis is done anhydrously with dry HCl gas being piped in.

The H2SO4 dehydration/rearrangement works, but only under pressure. At atmospheric pressures, the glycol gets etherified and escapes the reaction. There is a US patent somewhere on H2SO4 dehydration of simple glycols in a pressurized still.

Melgar - 1-4-2010 at 17:52

Quote: Originally posted by Lambda-Eyde

Eh, if I use cheap-ass buffered H2SO4 drain cleaner and CaCl2 driveway ice melter, it's not that expensive. I kind of like that reaction because it converts all the Cl and H ions to HCl and it goes slow enough that you don't get a room full of HCl vapors instead of getting them in solution. The CaCl2 + muriatic one is good too, although I don't think it's as efficient and it seems like you have to use a lot of CaCl2. But that stuff is cheap so who cares.

Quote:

Paint stripper is generally (at least in the UK) a blend of dichloromethane and methanol, so should still bear the "flammable" warning... you'll just have to read the label (this applies to wherever you are; theres nothing worse than buying something, attempting extraction and finding the desired material is not a component).

Yeah, that's true for the paint stripper here too, but I figured the methanol level must be comparatively low because the containers weren't marked as flammable. And yeah, reading the labels is always key.

Quote:

I'm pretty sure the Stephen aldehyde synthesis is done anhydrously with dry HCl gas being piped in.

Yeah, I post a more detailed explanation a few posts down.

Jimmymajesty - 6-4-2010 at 00:44

Hi folks!

If I were to make gaseous HCl I would pour 20w% HCl sol. into conc H2SO4 and distill off the gas, then lead it through a H2SO4 wash bottle to absorb traces of H2O, the H2SO4 then could be regenerated by heating.

I would not even attempt the CaCl2+H2SO4 method based on the Ca(NO3)2+H2SO4 experience, you will make an awfull mess for sure!

My problem is acetonitrile, I was a trainee once in an isocianate plant, acetonitrile was used as a solvent for HPLC uses, but I forgot to steal some..

I could buy DCM but it is expensive so I won't! BTW DCM based solvents is being drawn out from hypermarkets, at least in my country. I could buy it a year before or so, the methanol content was 10w%, but also there was a slurry layer on the bottom which was IIRC some kind of pine resin which during distillation solidifies maybe polyemrizes into the flask!

Melgar! you have all the necessary chems to give the procedure a try! so it is your turn!

Nicodem - 6-4-2010 at 00:59

If you only want a small amount of acetaldehyde you can just try with the Kornblum oxidation of ethyl bromide. Ethyl bromide can be made from ethanol, KBr/NaBr/NH4Br and H2SO4 (there are examples on the forum). Ethyl bromide reacts with DMSO fairly rapidly, so all you need to do is stir a solution of ethyl bromide and NaHCO3 in DMSO for a day at room temperature and then distil out acetaldehyde (mind the condenser cooling!). The Kornblum oxidation generally requires heating at 80-100°C for most alkyl halides, which is not an option for the volatile EtBr, but I think its reaction with DMSO to give the intermediate S-ethoxysulfonium ion, occurs at lower temperatures already.

Melgar - 6-4-2010 at 01:24

Quote: Originally posted by Jimmymajesty

Hi folks!

If I were to make gaseous HCl I would pour 20w% HCl sol. into conc H2SO4 and distill off the gas, then lead it through a H2SO4 wash bottle to absorb traces of H2O, the H2SO4 then could be regenerated by heating.

I would not even attempt the CaCl2+H2SO4 method based on the Ca(NO3)2+H2SO4 experience, you will make an awfull mess for sure!

Weird, I've done both reactions and they never gave me much trouble. The end result is CaSO4, aka gypsum. But it's gypsum as a powder which is easily washed out with water. Granted, the H2SO4 is a loss, but I found a pretty cheap local source ($10 a liter) so it's not a major problem.

I think heating the H2SO4/water/HCl mixture would give off a lot of fumes. But I guess you could send the vapors through any basic solution to minimize smells.

Quote:

My problem is acetonitrile, I was a trainee once in an isocianate plant, acetonitrile was used as a solvent for HPLC uses, but I forgot to steal some..

My problem is lack of ether. I have some, but it's definitely not very clean or dry, and probably is contaminated with water and ethanol. I'm trying to dry it using an aluminum amalgam, since that should theoretically work almost as well as sodium or potassium. It'd be nice if I didn't have to make it myself from Everclear.

As for the other two reactions, they both produce formaldehyde, and I want to try and make formaldehyde-free acetaldehyde so I can make sure I recognize the smell.

Lately I've been trying to make my own ethanol from distiller's yeast and sugar water. It's been a little tricky initially, especially hooking my distillation apparatus up to a practical boiler device. However, I did notice something VERY interesting. When it's hooked up, the first bit to come over smells identical to what I smelled when I ran ethanol vapors over copper oxide. No formaldehyde smell either. This makes sense, because these buckets have been sitting around for at least a month beyond when they were ready, as I've been trying to make time to distill them. They weren't airtight, so it seems plausible that oxidizing bacteria have gotten in and started to oxidize the ethanol to acetaldehyde. The next step would be acetic acid, but that has a higher boiling point and they probably haven't gotten there yet. If this really is acetaldehyde, this would be a really easy way to make it, although there would have to be a way to get it out of the ethanol/water/acetic acid that it's dissolved in.

By the way, the smell that I think is acetaldehyde is a sweet, fruity smell that smells vaguely like overripe plums. I'm still not sure how to get it out. Making an imine perhaps? But then, how to isolate the imine? And would it be especially temperature-sensitive?

[Edited on 4/6/10 by Melgar]

Melgar - 6-4-2010 at 13:37

Just did the acetonitrile reaction in ether, but even though it was successful, it was kind of a letdown to do all that work for a test tube half full of something that smelled like overripe plums. But anyway, I think that's the last time I'm going to do that reaction. I can make liters of the stuff by fermenting sugar in buckets and letting it oxidize beyond the initial fermentation. Plus, I learned that sodium bisulfite will react with acetaldehyde to form a precipitate. The precipitate can be made to release acetaldehyde by treating it with a base. You can probably get sodium bisulfite from brewing stores, but you can also make it yourself. I did. Basically, you have to bubble SO2 through an aqueous solution of Na2CO3. I got the SO2 by burning sulfur in a jar and having an aquarium pump pumping in fresh air, while the fumes were going out an exhaust pipe and into the Na2CO3 flask. It was a fairly cool and very easy reaction, while not being all that dangerous either.

Jimmymajesty - 8-4-2010 at 12:26

The case is the same with DMSO.. unfortunately i do not have any.

I think the best method would be ethanol dehydrogenation or catalytic oxidation, as there wold be no side products, (maybe some ethyl acetate and acetic acid which can be fractionated and used for something else). If croton aldehyde formed due to harsh reaction conditions it could still be used for making penataeritrithol.

I am not familiar with fermentation processes, but Melgar promised to try it out and post the results as his next experiment so I leave it for him

Be careful with yeast because it can easily overoxidize your desired product to acetic acid, and it will certinly do so in that conditions.

Yes saturated NaHSO3 (best if freshly made because it has the tendency to absorb oxygen) solution and acetaldehyde forms a crystalline compound which can be decomposed by adding a strong acid, the case is the same with cc NH3 solution, you can make aldehyde ammonia then release the aldehyde by adding H2SO4.
BTW in wine shops potassium metabisulphite can be bought which formula is K2S2O5, maybe you can convert it to KHSO3 by adding KOH I am not sure of that, I am also uncertain if K2S2O5 forms precipitate with aldehydes.

When pure sulphur is burnt SO3 forms too which makes a white smoke with atmospheric moisture, so your sulphite will not be purer than 92% of the theoretical at saturation (IIRC).

Oh! Have you identified the aldehyde by silver mirror test?

DJF90 - 9-4-2010 at 02:54

Metabisulfite hydrolyses upon addition of water: Na2S2O5 + H2O => 2NaHSO3

Melgar - 9-4-2010 at 03:16

I was going to do the silver mirror, but then I realized that I ran out of nitric acid to make silver nitrate with. And I left this big one-ounce silver coin I have at my girlfriend's house. So I'd like to try that test at some point, but I think the reaction with bisulfite would be proof enough. I finally just ordered some online because my stuff wasn't behaving, so I'll do that once it gets here.

DJF90 - 9-4-2010 at 03:58

You could also form the adduct with 2,4-DNPH, and take a melting point. IIRC, there are tables published in Vogel for such crystalline derivatives.

Jimmymajesty - 9-4-2010 at 04:21

Thx DJF90!

Melgar for your silver mirror tests you do not need to make silver nitrate, just use your silver coin as an anode in KNO3 solution, you will be amazed how fast the silver turns into Ag2O, then dissolve it in aq. NH3!

Jimmymajesty - 25-4-2010 at 13:33

I finally made some acetaldehyde in pure form!

I used the setup that I posted in my previous attempts, but this time I drew it for better understanding, sorry for the shitty line leading!

The glass tube was filled with copper oxide pressed into small granules of about the diameter of 3mm. Copper oxide was made with anodic oxidation, as it seemed to me that this way the oxide is extremely fine.

At the startup I gradually increased the temp of the khantal wire (setpoint of TC1) to 500°C, but the rate of acetaldehyde evolution is also acceptable at 400°C so I decreased the temp to 450 and kept at that. (the acetaldehyde is decompose @400°C to CO and CH4 but this was external temp control, so the temepature in the tube during operation is surely below 350C or so I think...)
It should be noted that I melted a small capillary, made of glass that protrude into the glass tube and tried to control the temperature that way (TC2), but as it turned out it was a bad idea and totally unnecessary. And I have not got a temerature controller with such a high response that this layout would require.

I directly avoided the heating of the catalyst, so the heating element(Khantal wire) and the catalyst bed was separated (Heating part~15cm, catalyst bed~15cm).

Identifying tests:

1 I led the gases into cc H2SO4! which was first get a yellow colour then got hot and charred after about 20min.

2 I led the gas into ammonical AgNO3 and heated it, a solid black precipitate was formed.

3 I led the gases into ccNaOH, first it got a yellow tint then turned into red and a tacky melted polymer with an apple like smell settled on the bottom.

4 The gas absorbs in aq ammonia and the solution on drying give a crystaline compound.

5 The NaOCl solution gets warm and turns yellow upon absorbing the gas.

6 If you drop some ccH2SO4 into the condensate (pure acetaldehyde) the condensate immediately starts boiling and if you do not stopper the bottle immediately you only get char, othervise you get two layers, a black layer at the bottom, and a yellow-white layer above it, which smells like pinewood three?!

7 I also lead the gas into Ca(OH)2 with HCHO followed the org synt volt 2 instructions, and after the required weight increase of the reaction mixture I poured some additional HCHO solution into it, (because the HCHO smell was totally disappeared after the addition), and got a yellow colour, which after keeping the mixture @ 45°C for an hour turned intense red. and a fine yellow powder settled at the bottom. (I did not have the time to isolate the product.....)

It seems to me that I forgot something, but I always have this feeling, anyways

So based on this reactions the dehydrogenation mehod, which is noted for lower by products, works at home, and can be reproduced by anyone..

After the tests, the setup was being run for additional 12 hours, during which I collected 69g of acetaldehyde, I poured it into a vial with a srew cap, upon opening the vial the liquid began to boil which is not literally means boiling, If you open the vial and follow a dust particle with your eyes you can see that it goes up and down, and a condensate on the vial walls can also be observed, furthermore on every opening of the vial I heared a 'shssssss'.

Which amazed me is that after the refrigerator there was still a lot of acetaldehyde uncondensed, I do not know how much, I can only say that the best is to use it as is, I am sure that I do not bother condensing it next time...

I will make some pentaeritriol and modify the setup to make acetic acid from ethanol with car exhaust catalyst (Pt on Al2O3) in my next project, wich I wanted for a long time, and after this success I seems to me that it wont be that hard

Any comments or improvements would be appreciated!

Attachment: acetaldehyde exp setup.rar (34kB)
This file has been downloaded 74 times

AceParkle - 2-5-2010 at 20:06

Quote:

While researching refractory materials I came across a high fired granular porous clay material which is used as an artificial soil for aquatic plants in decorative ponds and aquariums , as a substitute for ordinary gravel , and it occured to me that this might make a useful carrier for a catalyst . A similar material is a porous alumina which is used in water filtration as a substrate on which grow beneficial bacteria and algae , and this ceramic could be broken up into granules using a hammer , and the granules could also be useful as a porous substrate for carrying a finely divided catalyst .

I absolutely agree with your statement Rosco Bodine. Just like what I did and observed using the water filtration. It proves that this is very helpful carrier for a catalyst.

Melgar - 3-5-2010 at 12:32

I did the bisulfite adduct on some of the distillation product from my fermented sugar water. After a day or so, there was a fine precipitate on the bottom of the container, and the smell I recognized was gone. The trouble is, whenever I do a bisulfite adduct reaction, I always get just a tiny bit of the adduct, even if there's quite a bit in there. Here's what I do:

1. Add some sodium metabisulfite to denatured alcohol and wait for it to dissolve. Keep adding until no more dissolves.
2. Add the aldehyde solution to the metabisulfite solution. (metabisulfite solution is about 2/3 the total volume)
3. Wait for adduct to precipitate.

I'm not sure if I should just add bisulfite as the adduct falls out or what. And as I understand, metabisulfite needs water to turn into bisulfite. Maybe it takes a while for this to happen? In any case, it doesn't seem like you can actually find bisulfite that isn't metabisulfte, and if you order bisulfite, they send you metabisulfite. Also, I'm not sure what the adduct solubility is like. It seems to dissolve in methanol, but fall out in ethanol and isopropanol. Maybe it's different depending on the aldehyde. I've been testing with vanillin, since I can add a known amount of aldehyde and see how much precipitates, but I'm sure the other functional groups contribute to solubility.

Anyway, once I figure out how to do this reaction, I can quantify how much acetaldehyde I'm getting from fermentation.

Jimmymajesty - 3-5-2010 at 15:12

I also tried to coprecipitate the acetaldehyde with NaHSO3 but found it impractical, the NaHSO3 (Na2S2O5+H2O) is expensive and it is not really like Na2CO3+Ca(NO3)2, but for quantitative analysis purposes it may be usefull..

For purification of aldehydes see: http://www.sciencemadness.org/talk/viewthread.php?tid=10256#pid1220... Len1 post -Purification - stage 3- it contains a lot of usefull information.

I would distill off some liquid into cold ethanol out of the fermantation pot, an let is sit in a stoppered bottle filled with air under the sun for about a week, and smell it, if you cannot smell acetic acid, you only made very tiny amount of acetaldehyde.
I also did this experiment, but I poured some acetaldehyde into a prechilled PET bottle stoppered it and left it outside for about a week, the completion of the reaction could be seen on the shape of the bottle, after the addition of the acetaldehyde and closing of the bottle, the pressure increased inside it for about 0,5-1 bar, and after about a week the bottle was dented, upon opening it a strong smell of acetic acid could be smelled.

It should be noted however, that acetaldehyde is very volatile, when I tried to condense it @-20°C only part of the acetaldehyde condensed, despite of the very efficient chilling (the venting tube after the refrigerator was frosty) when I took a nosefull of the gases of the venting tube, the smell was still strong! Also, if you only notice an apple like smell, you only made ppm of acetaldehyde, It has a pungent odour, comparable with formaldehyde, but unlike formaldehyde its smell is pungent immediately after a nousefull of it..

Mildronate - 21-5-2010 at 11:31

I do acetaldehyde synth yesterday in mybody from vodka

Melgar - 21-5-2010 at 12:18

I remember the one girl I was dating once worked in a refugee center for mostly burmese refugees. The one Burmese guy that worked with her always had this strong smell about him that I couldn't place. Now I realize it's acetaldehyde. Guess he must have been quite the lush...

Jimmymajesty - 22-5-2010 at 08:54

I did two more experiments to make acetaldehyde
I electrolysed copper onto khantal wire, then heated it in air to oxidize the plated copper into CuO then placed the wire into a ketene generator (the setup was the same described in organic reactions), first the setup was running at dull read heat, then heated I presume the maximum that the khantal wire is able to resist to.
At the max temp, there was a lot of gas generation, it was so much that i could lit it and the continuous flame was about 10cm long.
So I can state that this is the fastest and easiest method to genererate a shitload amount of acetaldehyde!
If I have time in work, I will take a HS-GC-MS spectra from each pure sample collected at the two temperatures, and from the first, made by pressed CuO catalyst.

bbartlog - 22-5-2010 at 09:03

Without some isolation of the gas, you can't really say whether this was acetaldehyde. At higher temperatures (450+C) formaldehyde might predominate, or even smaller molecules. That said, I'm sure that if you can control temperature and flow rate adequately you should be able to generate useful quantities using your setup.

Globey - 23-5-2010 at 09:33

I don't know if it has been repeated upon, but alanine (simple amino acid) and not beta alanine I believe, will react with dilute HTH to form acetaldehyde. One might also want to consider just using a virgin catalytic converter, and dripping Everclear through that, at room temp, and having a condenser hooked up. The hexavalent chromium/dichromate reactions to me are really not so elegant, and I always like to stay away from anything polluting. Always go green if you can. Just my opinion. It's more elegant, and it's also the right thing to do.

john_smith - 4-6-2010 at 08:01

I just want to give you a way to make acetaldehyde. A very simple one is by heating a mix of Calcium acetate + Calcium formate. Both calcium salts are very simple to make.
The reaction is the following
Ca(HCOO)2 + Ca(CH3COO)2 ----> 2CH3CHO + 2CaCO3.

[Edited on 4-6-2010 by john_smith]

bbartlog - 4-6-2010 at 09:16

Hm, yes. But have you actually tried this? I don't doubt that some acetaldehyde does get produced (I see for example http://www.nature.com/nature/journal/v165/n4193/abs/165402a0.html supports your idea), but depending on temperature, heating rate, admixture and so, different proportions of products would result. I recommend http://www.scribd.com/doc/28118713/Thermal-Decomposition-of-Metal-A... , not for insight into this particular proposed way of making acetaldehyde but just for some idea of the variety of possible reactions (and by extension the need for fractionation and workup).

Jimmymajesty - 10-6-2010 at 06:34

Here are the HSGC MS results of the two samples made by completely different apparatus.. to my deepest suprise.. the composition of the two samples are identical.. eeh!!

5micro liter of the pre chilled stuff with a chilled syringe was injected to a HS ampoule and heated to 300°C the absorbing component of the GC tube was of poly ethylene glycol.

The components on the main spectrum in ascending order of the retention time:

Acetaldehyde: 1,93 min.. I can say.. that lab quality acetaldehyde can be made at home which is just awseome :cool:

Acetone: 2,17min

Butanal: 2,45min

Ethyl acetate: 2,513min

Diethyl acetal: 2,54min

Then: 2 butanon, ethyl alcohol, paraldehyde (4,8min), metaldehyde, dioxolane.

I would like to add that I used denaturated alcohol, which is mainly adulterated in my country with methyl ethyl ketone (2 butanone), that explains the 2 butanone peak, the ethyl alcohol peak is evident

Also I would like to add that more acetaldehyde can be produced by the lamp method according to the results, but it can be attributed also to error of measurements, I mean messing with prechilled 5micro litre syringe can really cause difference at paralell measurements.

More ethyl acetate is produced by the lamp method due to higher temperatures, also the amount of paraldehyde and the tetramer is more that I cannot explain taking into consideration the increase in the amount of ethyl acetate, these impurities are only a few percent of the total sample though.

Based on the results both setups are recommended for a trial to every home chemist

Acetaldehyde keten lamp vs tube reactor.JPG - 94kB

Melgar - 11-6-2010 at 14:20

Actually, I tried mixing calcium hypochlorite pool shock and alanine (from nutrition stores) and I have to say, this has got to be the easiest way by far to make small amounts of acetaldehyde. Look up "Strecker degradation" to see how the reaction works. I've also heard, though I can't verify it, that TCCA pool shock will give the corresponding nitriles rather than aldehydes.

Ephoton - 11-6-2010 at 20:08

you are right there meglar TCCA makes nitriles from aminoacids very easily.

thankyou very much to both your self and jimmymajesty for pointing out another use for alanine
and a ketene lamp.

peach - 19-6-2010 at 17:36

JIMMY! Great experiment! I was going to suggest something similar, but don't have that kind of analytical equipment to hand. I've seen people rabbiting on about the idea of building mini catalytic reactors but rarely hear about practical attempts and have never seen a spectrum from one.

I'm kind of busy and can't read back to your other posts right now, but did you try depositing the copper onto zeolite for the cake? This is mentioned all over the patents regarding copper catalysts, as well as how trace impurities in the copper affects the process. Like, I think zinc helps produce MEK or butanal in the product, or something along those lines.

From memory, they use ?ZSM-10? zeolite as the support. The vast surface area the structure presents accelerates the catalysis. The specific pore size seems to also influence the selectivity of the process.

Of coarse, the patents also discuss how they deposited the copper from solution (easy stuff). Google around "ethanol copper zeolite patent" and you'll be underway in no time.

DCM, I've never seen bearing a flammable sticker in real life. I have a tank of paint stripper, a container of pure DCM for everyday solvent cleaning and an up to date reagent grade bottle from a laboratory supplier. None of them have flammable stickers. But it has now been upgraded to a potential carcinogen. Meaning it can have a skull and cross-bone sticker in place of it's old harmful cross. I bet all the older chemists aren't impressed! I'm not! Hopefully it's not another benzene. I haven't seen these stickers on paint stripper yet, which is odd as they are very high concentration sources of the solvent. They're still using the harmful sticker on both stripper and the reagent bottles.

I have a bone to pick with people constantly referring to things as toxic, when they're actually more like harmful. It seems anything with the potential to cause any harm is upgraded to toxic now. Whilst things that do present real risks (like cancer) still have a harmful sticker on them. Since irritant also exists, it makes me question precisely what harmful is still being used for by these people. To me, toxic means it creates a long lasting risk at everyday exposures. So benzene would be toxic to me, as it damages DNA and creates a long lasting, carcinogenic risk. DCM would fall into the same category for myself. Following that pattern of logic, I'd nominate DCM for a harmful cross (with harmful / irritant under it) and a skull and cross-bones (with carcinogen under it), as it is both immediately irritating and slightly dangerous in terms of exposure but also capable of longterm damage. Cyanide would be harmful, as (despite it being extremely dangerous) it does not accumulate or present a longterm risk. I would seriously love for them to produce a new sticker visually indicating something is a suspect carcinogen, like a simple double helix (or to write this under the skull and cross-bone, as they already do under the blanket, seriously outdated term poison). I would also like to see the NFPA 704 rating system used on the containers. It's on the sides of the trucks, it should be on the containers people will actually be handling. I worry when I see MSDS that take the safe route out and blanket list everything as dangerous to cover against liable action. It's like saying a relatively harmless drug is in the same category as heroin. Causing users of the former to think the latter will be the same in terms of risk. Failing those changes to the stickers, or in addition to them, I'd like to see an accumulation sticker to indicate whether acute exposure is going to build up. And I want all of those changes regulated by someone other than the chemical companies, who will plaster them all over everything as the carcinogens start lining up. Either way, what I'm saying is that I'm not happy with the level of information the quick references provide, and think it could easily be improved upon. And students should be taught precisely what each of the few new variations means.

In terms of extracting DCM from paint stripper, get the cheapest, nastiest stuff you can. They usually have more DCM in them. It's usually around 50-70%. It will also be mixed with a polymer to make it thick enough to paint onto vertical surfaces without it immediately running off or evaporating away. Before you distill it, wash it with some water. The water should start looking like someone's cum in it. There'll be opaque white goo floating around in it (the polymer). Throw out the wash, distill the remaining organic. Using a saline wash may help prevent loss of DCM, as some of it will end up in the aqueous phase using pure water. If you go straight to distillation with the polymer, you may cake it onto the flask. It boils like crazy under only moderate vacuum, but it's also not going to liquefy at the condenser all that well, so it'll end up spitting out the pumps exhaust. Go with atmospheric distillation given that it boils so close to body temperature and doesn't break down. It's a fairly 'fun' distillation given how easy it is compared to oxygen sensitive, high BP things that bump under vacuum.

Bulk pyridines from a catalytic reactor? One thing that really interested me about this method of producing aldehyde was that the product is part of the one pot pyridine synthesis (throw it all together, stir away). One can cheaply and easily ferment hundreds of liters of ~20% alcohol at home in a week or two using raw sugar and distillers yeast. The excess water can be quickly and cost effectively stripped by dumping in a bag of plaster I believe, then decanting from the cake. The remaining liquid can then yield 100% ethanol under a more reasonably sized vacuum distillation (which breaks the azeotropic mix). You could also simply warm up the drum with an immersion heater (even the plastic ones will take the heat) and gently strip the azeotrope off, then run it through a smaller volume vacuum distillation in the glass. Homebrewers of moonshine go as simple as putting a plastic bucket of alcohol inside another plastic bucket with a lid and then warm up the alcohol containing bucket, letting the azeotrope condense on the sides of the outer bucket. Catalytically produce aldehyde from the vacuum distilled azeotrope, feed it into the one pot. I wonder if this same catalytic method works for methanol to formaldehyde (another component of the one pot). Yes, I know about the niacin method. But this seems reasonably realistic if you wanted larger volumes of pyridine. Or, for myself, just for the fun of doing something involving both biology and chemistry. I've brewed up huge volumes of alcohol using distillers turbo yeast and raw sugar in a big 210l plastic storage drum with an aquarium heater. The drum was formerly used to internationally transport olives. Yum!

And even featured a very nice screw on lid that could easily be ported for an air pump, lock or vapor outlet; with your condenser possibly being as simple as a roll of PB / PEX plastic plumbing pipe, secured to the lid using a push fit cold header tank connector (they sell them specifically for this pipe and they feature a rubber gasket). I just loosely put the lid on and let it go. It was so tough I could kick it around the floor and barely scratch it. It all cost next to nothing and took next to no effort. I 'sterilized' with a quick rinse of boiling water. I rolled the culture up in a 15l container before hand, using more clean methods (e.g. boiled water), then inoculated the 210l of water at 50% of the recommended sugar concentration, so as to avoid thermal death. Then poured in the remaining 50% once it had calmed down a little. I was using 25kg sacks of sugar from a bakery supplier (real, real cheap). The water in the bulk drum was straight from the tap. The rate of fermentation was hilarious. You can also yield other useful building blocks, solvents and reagents from the process. It's like a total synthesis, but without the total overkill. The appeal of going from something as simple as sugar, water and yeast is high for myself. In addition, yeasts can perform other interesting feats of biochemical manipulation. And the raw product of this method is a highly valued resource for those who enjoy getting very drunk, very quickly, very cheaply. Might I suggest sampling some 100% ethanol, or buying a nebulizer and blowing O2 through it at the same time (you could use the pump that comes will a full kit for aerating the fermentation, not that it really needs it, but it might help churn up the mix). Caution, ethanol + pure O2 + drunk people = extreme fire hazard. These methods would also be very easy to lay down at the small scale, starting from some off the shelf alcoholics grade, no name vodka. The fermentation is bulletproof, it's about the oldest, most well studied biochemical method committed to text. You'd yield around 40 liters of 100% ethanol from a 210l drum fermentation. And foaming isn't an issue at all given how simple the sugar supply is; it doesn't foam. I also doubt you'll get into that much trouble, if any, distilling your own alcohol if you can demonstrate that it's not intended for consumption (which is what the tax is there for). When it comes to chemicals, the law is more concerned with why you have it and how safely you can handle it rather than the fact you have it in the first place.

[Edited on 20-6-2010 by peach]

mr.crow - 20-6-2010 at 11:32

Quote: Originally posted by Ephoton

you are right there meglar TCCA makes nitriles from aminoacids very easily.

I requested a reference for this in the references section. You need pyridine tho

peach - 20-6-2010 at 17:47

Quote: Originally posted by mr.crow

Quote: Originally posted by Ephoton

you are right there meglar TCCA makes nitriles from aminoacids very easily.

I requested a reference for this in the references section. You need pyridine tho

See! Everyone loves pyridine!

watson.fawkes - 20-6-2010 at 20:57

Quote: Originally posted by peach

I have a bone to pick with people constantly referring to things as toxic, when they're actually more like harmful. [...] Cyanide would be harmful, as (despite it being extremely dangerous) it does not accumulate or present a longterm risk.

Under this theory, cyanide would be non-toxic. Because this is the internet, I will point out explicitly that this is absurd. Just as you don't get your own facts in an argument, you don't get your own language in public discourse. That is, unless you are in discourse with Tweedledee and Tweedledum; with them you can say anything you like.

Jimmymajesty - 20-6-2010 at 23:29

I also read patents how to make catalysts that for example increase the ethyl acetate yield, but I think the only product of value of catalytic dehydrogenation of ethanol is acetaldehyde, if I were to make ethyl acetate I surely will not make it this way.

The making of some hundred of pressed copper oxide pellets was really a pain. I was glad when I finished, that I will not have to in my rest of my life. I have the shivers of the simple thought of a 4%Zn 6%Mn 10%Co 80%Cu homemade catalyst, but If you have the time to make it I will be happy to try it out

I took a photo about the CuO catalyst, (before and after shots)
I also took some catalyst pellets after a 12 hours of run and broke them to show that also the inside parts are reduced, so It must be porous.

Attachment: CuO catalyst.doc (96kB)
This file has been downloaded 26 times

[Edited on 21-6-2010 by Jimmymajesty]

peach - 23-6-2010 at 16:56

Quote: Originally posted by watson.fawkes

Under this theory, cyanide would be non-toxic.

It'd be classed as harmful, since it neither accumulates or causes permanent damage; it actually burns off quickly compared to other chemicals. Alcohol and tobacco (do they have a chemically additive sticker?

) are both harmful and toxic at levels that are used everyday by vast numbers of people. They are also both flammable, alcohol for obvious reasons and cigarettes because they contain burn enhancers. They are responsible for hundreds of millions of deaths and they lack all three labels. As is table salt lacking it's harmful / toxic sticker due to the heart disease it causes when exposure is at realistically prominent, everyday excesses.

Quote:

The making of some hundred of pressed copper oxide pellets was really a pain. I was glad when I finished, that I will not have to in my rest of my life. I have the shivers of the simple thought of a 4%Zn 6%Mn 10%Co 80%Cu homemade catalyst, but If you have the time to make it I will be happy to try it out

Could you not skip the pelleting by depositing it onto a granular zeolite? Which'd also increase your surface area by orders of magnitude.

[Edited on 24-6-2010 by peach]

Sedit - 23-6-2010 at 19:00

The reference now in the RRthread speaks of using DILUTE HNO3 to generate an aldahyde from an alcohol. Mainly they speak of Benzaldahyde from BnOH but it could be adapted rather well for acetaldahyde. Im currently working with it to oxidise all the was to AcOH but the smell of Acetaldahyde is very very strong. After a period of ageing the mix one could just distill off the aldahyde or precipitate as the adduct.

jon - 23-6-2010 at 22:16

cyanide became safe to handle??
did i just read that????
or am i on drugs?

Sedit - 24-6-2010 at 07:59

Well you sort of read that but yes you are on drugs...

Peach was arguing the semantics on the usage of calling a compound to toxic(accumulates in the body such as Hg) and harmful(death on the spot like H2S or HCN)

watson.fawkes - 24-6-2010 at 08:11

Quote: Originally posted by jon

cyanide became safe to handle??
did i just read that????
or am i on drugs?

You are illustrating why changing ordinary language usage into jargon is completely dangerous in this case. The reason for labeling compounds toxic and harmful is that these words are meaningful in an ordinary sense to ordinary people. If you use these meanings in some jargon-laden way, it not only fails to communicate, but communicates something that is other than truthful.

peach - 28-6-2010 at 08:48

They're now planning to use H2S for a form of suspended animation of seriously injured casualties on the way to surgery. They worked out that a very precise dose of H2S antagonizes (blocks) the sites that would be damaged by oxidation when normal homeostasis wasn't functioning. They've been testing it on mice and the results are so positive they're going to human trials. I think they'll be injecting it dissolved in solution. The 'victim' also needs cooling in an ice bath.

I don't want to start arguing, but it's somewhat ironic you're calling it jargon when you'd likely have a fit on me if I started using none standardized names for reagents and solvents. I know what you're saying, but I think jon is joking.

He's actually illustrating my own point perfectly well. In that people now assume harmful means safe to handle. Whilst genuine lab suppliers are still shipping things that should now be labeled toxic as harmful. It may as well not exist as a label.

And I know none of this has anything to do with aldehydes and I hope I haven't annoyed you. I didn't mean to do so if I did, I just don't like the blanket use of the word toxic, as it desensitizes people to the real risks. I'll shut up now.

[Edited on 28-6-2010 by peach]

Reference - 18-7-2010 at 02:41

Just a thought, if you can get your hands on a Selenium compound,
acetone reacts with selenium dioxide to make an aldehyde.
O=CH-CO-CH3
http://www.transtutors.com/chemistry-homework-help/aldehydes/oxidat...
You could protect the aldehyde by condensing with NH4OH, leaving the ketone vulnerable to be reduced (for example with hydrogen iodide) but then I am unsure of how to recover the aldehyde again, after it has condensed. Maybe reacting with NaOH will give off ammonia gas and make NaOCH(OH)-CH2-CH3 , then acidify to recover the aldehyde.

Melgar - 20-7-2010 at 19:28

Treating amino acids with bleach does indeed produce aldehydes, for example, alanine + bleach gives acetaldehyde. However, this reaction also produces CO2 and NH3, and the NH3 is chlorinated into one of the chloramines. Still not entirely sure how to get rid of those...

Jimmymajesty - 21-7-2010 at 11:29

I never succeeded in recovering the acetaldehyde from dilute solutions, I usually got an unpleasant smell, that is far away from the smell of pure acetaldehyde. Also the acetaldehyde does not like to be acidified/basified

you will get either a yellow solution with and acrid smell or an orange sticky polymer with an apple like smell, depending on the pH that you disturb poor little CH3CHO molecule

rrkss - 23-7-2010 at 02:07

Quote: Originally posted by Hoveland

What is the reaction with acetaldehyde when the pH goes to high or too low?
I found an excellent explanation about aldehydes: http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/aldket1.htm
which did not seem to tell what these reactions might be, but as a side note, I did learn

"Although the addition of water to an alkene is exothermic and gives a stable product (an alcohol), the uncatalyzed reaction is extremely slow due to a high activation energy . The reverse reaction (dehydration of an alcohol) is even slower, and because of the kinetic barrier, both reactions are practical only in the presence of a strong acid."

Look up aldol condensation for part 1. Part 2 of your response has nothing do do with aldehydes or acetadlehyde.