Sciencemadness Discussion Board

Acetaldehyde synthesis

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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 5233 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 C2H6O and H202 plus a catalyst will make acetaldehyde.

C2H6O + H202 + HNO3

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 :D

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 :P

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 <i>dehydration of tartaric acid by distilling with potassium acid sulfate</i> so both decarboxilation and pinacol rearrangement happen in this reaction. just needs wine lees (so fucked, all alcoholic drinks are forbidden here!:o:()
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:D 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.:o

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 <i>lab</i> 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.:D 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)<sub>2</sub>;) and ketones (e.g. CH<sub>3</sub>COCH<sub>3</sub> with Ca(OOCCH<sub>3</sub>;)<sub>2</sub>;). Btw, I chose calcium because CaCO<sub>3</sub> is so readily available to me in the form of... chalk! :P Easy to crush up, and all.

I then got into the "double salts" (correct phrase?), such as Ca(OOCH)(OOCCH<sub>3</sub>;). If this could exist, even in small amounts where distillation would be required, one could theoretically make acetaldehyde via:
CaCO<sub>3</sub> + HCOOH + CH<sub>3</sub>COOH <s>&nbsp;&nbsp;&gt;</s> Ca(OOCH)(OOCCH<sub>3</sub>;) + CO<sub>2</sub> + H<sub>2</sub>O
Ca(OOCH)(OOCCH<sub>3</sub>;) <sup><u>&nbsp;&nbsp;<font face=symbol>D</font>&nbsp;&nbsp;</u></sup><s>&gt;</s> CaCO<sub>3</sub> + CH<sub>3</sub>CHO

If you need HCOOH, you could always use oxalic acid (maybe from Zud cleaner) and glycerin by using <a href="http://www.rhodium.ws/chemistry/formic.acid.html" target="_blank">this method</a>. <a href="http://www.rhodium.ws/chemistry/grignard.formic.html" target="_blank">This</a> 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 :o
so I hope the logins here are not IP specific :D

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 :D 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 :D

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 :D 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 :D

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 ;)


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? :o

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&a...

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 :D 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 :o :D:cool::D 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?
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