Sciencemadness Discussion Board

Acetaldehyde synthesis

 Pages:  1    3    5

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 969 times

AceParkle - 2-5-2010 at 20:06


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: 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 :D

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 supports your idea), but depending on temperature, heating rate, admixture and so, different proportions of products would result. I recommend , 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! :D 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! :D

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 865 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? :D) 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.


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. :P

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.
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:
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.

Practical Preparation

future625 - 8-1-2012 at 22:04

that I know of there are 3 practical benchtop methods of preparing acetaldehyde; Namely the dehydrogenation of ethanol, the dehydration of ethylene glycol and Oppenauer oxidation.

1. My favorite and first goto would be the Oppenauer oxidation of absolute ethanol with aluminum isoproproxide in acetone. I would make the abs. EtOH by drying Everclear over plaster of paris. One could get everything at retail around town!

2. Dehydration of glycol is a combustion tube method. vapor phase ~400`C. essentially it gives 65/35 either way of 1,4 dioxane and acetaldehyde. alumina and Al phosphate are catalysts. can be made selective for either product by catalyst choice.

3. Dehydrogenation of ethanol with oxidative option. essentially one passes ethanol vapor through copper tubing packed with copper wool or BB's about 30% is converted to acetaldehyde and hydrogen. the temperature is ~280-300`C or 260-290 etc this could be achieved w fiberglass cloth, nichrome resistance wire and then fiberglass batting for insulation. This is an endothermic reaction. preferred catalyst is copper sponge; copper oxide, and copper chromite are active as are others

3b the oxidative option, one blends air with ethanol vapor, the O2 consumes H2 and drives the hydrogenation equilibrium towards the products While supplying process heat to boot.

Overall, I highly recomend No. 1 over all others. Oppenauer oxidation is suitable for preps on the order of a Kg. methods 2 and 3 are barrel size batch benchtop preps, I wouldn't consider using them for batches under a gallon, and probably wouldn't bother unless batch size was greater than 5 gallons.

Adas - 9-1-2012 at 08:59

My favorite is to dehydrogenate ethanol - Put pressed copper wires into a glass tube, heat it using induction heating (to not waste gas + this is ineffective) and pass ethanol vapor through it. I find this method the best.

future625 - 11-1-2012 at 12:48

Im a big fan myself. I've been thinking about how ethyl acetate in ethanol would work out, subjected to the copper tube.

ksj_6808 - 13-9-2012 at 23:14

As for what ive read on the acetaldehyde the most practical way of making this would be either oxidation of ethanol through a mild oxidiser such as the dichromate in 23% sulfuric acid or oxidation through copper or platinum (not sure on this one though). Type in "Acetaldehyde synthesis erowid" in google and click on the one that goes to the erowid site. This seems very logical, basically a distillation apparatus is set up, and 23% sulfuric is placed in the boiling flask, then an addition funnel is connected to the boiling flask with ethanol/water/sodium dichromate, the sulfuric is heated just enough to boil and the solution in the sep funnel is slowly dropped in, and the heat can be turned off because the reaction makes its own sufficient amount of heat and the acetaldehyde/other products are distilled over, then the crude acetaldehyde is put into a reflux setup, basically just refluxing and bubbling the vapors off of it through ether. The wash bottle is basically an enclosure where a gas line leads to it from the top of the condenser and it bubbles through the solution of ether, then that bottles exit gas nipple is connected to another wash bottle with ether ect ect...just go read it. Anyways i've seen a red hot copper rod stuck into a beaker of ethanol and supposedly it converts the ethanol into acetaldehyde which might be too much oxidation...Im pretty damn sure the dichromate way works, i've read quite a bit on it. IF YOU CANT GET SODIUM DICHROMATE AND YOU LIVE IN THE USA, THEN YOUR EITHER DUMB OR SOMETHING, ITS CALLED EBAY!!! Also its sold in solutions for electroplating.

weiming1998 - 14-9-2012 at 03:14

I have made acetaldehyde as a concentrated solution in water by adding calcium hypochlorite to excess ethanol in a flask, then adding a stopper on and heating a bit. The reaction goes very fast, and is exothermic, to the point that runaway can occur in large amounts. producing a fruity-smelling gas that dissolves fully in water. This gas is acetaldehyde because on reaction with further calcium hypochlorite, filtration, then boiling and acidification, formic acid is produced (the resulting liquid is very pungent and stings the nose).

Lithium - 14-9-2012 at 13:28

Yes, i too have performed the oxidation of ethanol with calcium hypochlorite. I think it is a very scary reaction in the respect that it can run away very easily. When i am performing it, i add solid 70% calcium hypochlorite to the flask and add the ethanol all at once. i frequently put the flask in a ice bath as i fear it will explode or start to boil the ethanol along with it. once the icebath is added, the reaction seems to stop, and no more acetaldehyde is produced. once the ice bath is removed and a small flame is applied, it vigorously restarts, producing copious amounts of acetaldehyde gas. this gas can be passed through a CaCl2 drying tube and then bubbled into a cold solution water, ethanol, dichloromethane. sometimes it is hard to see if all the Ca(OCl)2 has been used, as after the reaction has complete, there is a CaCl2 brick at the bottom of the flask. it seems it would be wise to utilize an addition funnel to slowly drip the ethanol into the flask, as to ensure even bubbling and smoother/safer reaction.

borrowedlawyer - 8-10-2012 at 02:17

Quote: Originally posted by jon  
cyanide became safe to handle??
did i just read that????
or am i on drugs?

Cyanide compounds can be safely handled (this is true with almost anything), provided adequate precautions are taken. However, most are very toxic, as you already know.

[Edited on 8-10-2012 by borrowedlawyer]

Help! PCC method...

cold_electrician - 8-10-2012 at 11:17

Hello all, I'll begin with the formality of introducing myself as "a long-time lurker, 1st-time post-er". I have a question which should be simple, but I can't seem to find a proven, precise method on ANY search engines... Lots of theory and stoichiometric equations, but nothing specific enough for me to confidently proceed... So here goes:

I've succeeded with the pyridinium chlorochromate (PCC) prep, and am ready to oxidize my dry ethyl alcohol; I intend to use celite, silica, 4A sieves. I've read all the literature I could find for oxidizing primary alcohols to aldehydes, but it seems like nobody's bothered to describe a specific workup procedure, since its such a straightforward reaction. I don't want to waste my reagent! Not a fan of CrO3 :(

Can anyone point me in the right direction? I've got an arsenal of pure, dry solvents to chose from, EXCEPT that I lack diethyl ether... just have petroleum ether(s) available.

The original paper [Tetrahedron Letters, No. 31, Corey, E.J. and Suggs, W., 'Pyridinium Chlorochromate...'] describes a TINY-scale procedure, with 1.5mmol PCC in 2mL DCM, and '1 mmol in 0.5 to 1.5 ml of CH2Cl2' of Alcohol X...

Does anyone have experience with this? I'm not comfortable with blindly scaling-up the given molar ratios; I'm thinking more along the lines of ~1mol of PCC.

Any help would be greatly appreciated, and I'd be glad to post results and pics.

tetrahedron - 8-10-2012 at 12:53

Quote: Originally posted by cold_electrician  
I've succeeded with the pyridinium chlorochromate (PCC) prep, and am ready to oxidize my dry ethyl alcohol; I intend to use celite, silica, 4A sieves. I've read all the literature I could find for oxidizing primary alcohols to aldehydes, but it seems like nobody's bothered to describe a specific workup procedure, since its such a straightforward reaction. I don't want to waste my reagent! Not a fan of CrO3 :(

Can anyone point me in the right direction? I've got an arsenal of pure, dry solvents to chose from, EXCEPT that I lack diethyl ether... just have petroleum ether(s) available.

hi cold_electrician.

i think the reason you can't find a detailed write up is that the PCC prep is only a general method for preparing small quantities of aldehydes from new alcohol compounds. it certainly isn't meant to provide a routine acetaldehyde synthesis.

note that petroleum ether is not a true ether and is completely different in properties from diethyl ether. but if they say DCM anyway..

Magpie - 8-10-2012 at 17:29

Here's an excerpt from OrgSyn. You can find it yourself by searching with the term pyridinium chlorochromate:

B. General oxidation procedure for alcohols. A sufficient quantity of a 5% solution of dipyridine chromium(VI) oxide (Note 1) in anhydrous dichloromethane (Note 7) is prepared to provide a sixfold molar ratio of complex to alcohol, an excess usually required for complete oxidation to the aldehyde. The freshly prepared, pure complex dissolves completely in dichloromethane at 25° at 5% concentration, giving a deep red solution, but solutions usually contain small amounts of brown, insoluble material when prepared from crude complex (Note 8). The alcohol, either pure or as a solution in anhydrous dichloromethane, is added to the red solution in one portion with stirring at room temperature or lower. The oxidation of unhindered primary (and secondary) alcohols proceeds to completion within 5 to 15 minutes at 25° with deposition of brownish-black, polymeric, reduced chromium–pyridine products (Note 9). When deposition of reduced chromium compounds is complete (monitoring the reaction by GC or TLC is helpful), the supernatant liquid is decanted from the (usually tarry) precipitate, which is rinsed thoroughly with dichloromethane (Note 10).
The combined dichloromethane solutions may be washed with dilute hydrochloric acid, sodium hydrogen carbonate solution, and water, or filtered directly through a filter aid, or passed through a chromatographic column to remove traces of pyridine and chromium salts. The product is obtained by removal of dichloromethane; any pyridine that remains can often be removed under reduced pressure.

[Edited on 9-10-2012 by Magpie]

Dr.Bob - 8-10-2012 at 19:29

Quote: Originally posted by cold_electrician  

Does anyone have experience with this? I'm not comfortable with blindly scaling-up the given molar ratios; I'm thinking more along the lines of ~1mol of PCC.

I wouldn't start at 1 mol, I would start at maybe .1 mol to test the chemistry first. Isolating the aldehyde will be tough, due to the BP, many people would just go ahead and use the solution of aldehyde in DCM after perhaps filtering through Celite and some silica gel to remove the PCC salts. You could distill the aldehyde and condense with a dry ice cooled condenser (or at least salt and ice.) if you want to purify it, but it is not easy to keep around.

DJF90 - 9-10-2012 at 07:12

You can store acetaldehyde as one of the polymeric forms, either the trimer paraldehyde (produced with sulfuric acid catalysis IIRC) or the tetramer metaldehyde (with hydrogen halide catalysis). In some cases they can be used as an in-situ source of acetaldehyde.

hissingnoise - 9-10-2012 at 07:30

I don't know the metaldehyde content of slugkiller pellets but heating to ~80°C breaks the tetramer so that acetaldehyde might be (carefully) distilled from the material!
The pellet's fruity smell is that of the aldehyde . . .

hissingnoise - 9-10-2012 at 07:53

All things considered though, hydration of C<sub>2</sub>H<sub>2</sub> is most convenient if one doesn't have ethanol to hand . . .

cold_electrician - 9-10-2012 at 11:19

Many thanks! The OrgSyn description with Collin's Reagent is the best workup I've seen, but the reason I chose PCC was to avoid the "sixfold molar ratio of complex to alcohol", and of course, because of the resources which I personally have access to.

I've read that PCC can be used in near-stoichiometric amounts? I'd certainly use an excess, which is always recommended, but my impression is that one of the main advantages of PCC is that lower quantities are required.

Dr. Bob, I think I'll start out with the .1mol suggestion, and do a couple preliminary trials, "scientific method" style. You hit the nail on the head regarding the issue of isolation - I definitely want to use (immediately!) a solution w/ DCM - not trying to test the stability of acetaldehyde in storage.

And if all else fails, slug poison.

Dave Angel - 9-10-2012 at 12:13

Quote: Originally posted by hissingnoise  
I don't know the metaldehyde content of slugkiller pellets but heating to ~80°C breaks the tetramer so that acetaldehyde might be (carefully) distilled from the material!

I looked into this one a while back and will likely revisit. For current reference (as I'm sure it is known) you can buy pellets at somewhere between 1 and 3 % metaldehyde depending on brand, and I've found a concentrated suspension at 20 % in more serious garden centres.

I tried a couple of rough depolymerisations of the 20 % suspension and succeeded mainly in subliming metaldehyde into my condensor coil, probably by heating too rapidly. Actually, perhaps one would be wise to sublime the material first to obtain the pure metaldehyde in case there are impurities inhibiting depolymerisation.

Furthermore, I stored the depolymerisation mixes in a flask, intending to continue the attempt, left it for months and came back to find some acetaldehyde in solution. I managed to distill this out with some serious cooling (the likes of an ether condensor) and a heavily chilled ice bath for the receiver.

So essentially, one route is to dilute the metaldehyde in a low concentration of sulphuric acid, stick it in a bottle for months and forget about it, and then distill the result when you have a lab tidy. Caveat: this was very rough, undocumented work so YMMV. Thermal depolymerisation, as hissingnoise suggests, is likely a more elegant route.

hissingnoise - 9-10-2012 at 13:05

It's also, unfortunately, a slow process and the 20°C B.P. doesn't help.
Hydration of ethyne in dilute sulphuric acid with mercuric sulphate catalyst at ~80°C with a well chilled receiver to condense CH<sub>3</sub>CHO should work well!
Impurities in carbide-produced ethyne will eventually poison the catalyst but it's still a usable process in the lab.

BTW, I should say I haven't actually tried either process . . . yet . . .

S.C. Wack - 9-10-2012 at 16:24

How many grams of acetylene in a #3 cylinder?

Magpie - 9-10-2012 at 18:31

Quote: Originally posted by S.C. Wack  
How many grams of acetylene in a #3 cylinder?

A website says a #3 cylinder contains 75 ft^3 of acetylene. Without attempting to make any correction for temperature this would be:

wt. = (75ft^3)/(359ft^3/lb-mole)[(26 lb/lb-mole)][454g/lb] = 2466g

S.C. Wack - 9-10-2012 at 19:01

I assumed those numbers were the actual volume of the cylinder, I don't know how, it's obviously not...well if the cylinders are all filled by weight why aren't those weights listed on the internets (they'll say the acetone weight).

I guess it's not bad if you already have a tank...or don't but want to make a lot of paraldehyde. I've always wondered why it's addictive.

[Edited on 10-10-2012 by S.C. Wack]

Acetaldehyde from Acetone

ScienceHideout - 21-11-2012 at 08:07

I looked in the search engine at the topics of acetadehyde- and I was surprised that no one brought up vapor phase oxidation of acetone. It sounds like it is one of the most straight forward procedures, although I doubt that the yield would be good. However, with how cheap acetone is- why not try!?

Check this out:

The only thing that I can't quite figure out is how to capture the acetaldehyde that is formed. Perhaps we can condense it along with acetone, convert it to the trimer, and reproduce te acetaldehyde?

Please reply if you have any ideas. Thanks!

The_Davster - 21-11-2012 at 08:28

Bisulfite adduct.

Substitution of Sodium Dichromate

ScienceHideout - 22-11-2012 at 09:19

As you all know, this week I am especially obsessed with acetaldehyde- and I would like to make some of my own :D

This looks like the best and most productive way I've seen so far.

Problem- I don't have any sodium dicromate

Possibilities: I have ammonium dichromate. If I adjust the stoiciometry- could this work? I also have potassium chromate. I know acids convert this into a dichromate. If K dichormate will work, can I just throw some extra acid in solution 1 and hope it works?

Thanks in advance!

tetrahedron - 22-11-2012 at 15:04

Quote: Originally posted by ScienceHideout

that looks like a half-assed school report. they list eight (8) synonyms for water..

[Edited on 22-11-2012 by tetrahedron]

ScienceHideout - 23-11-2012 at 07:46

So? Even if it is a school report, it is a valueable resource. The author of this has quite a few other respectable documents. Of course, not as venerable as an O-Chem text book, but in my mind- this procedure it describes is useful.

I have seen other sources that use dichromates to make acetaldehyde from acetone- so why do we have to declare that this is half-assed becuase it lists 8 synonyms for water? :)

bbartlog - 23-11-2012 at 16:15

It is half assed for other reasons. Personally I find the bizarre bulking up with tabular information about all the different compounds to be the most objectionable; seven pages of mostly irrelevant info about water, H2SO4 etc. (including photos!) and then various sorts of critical information is missing from the experimental. No sizes are given for any of the apparatus, no temperatures proposed or measured, no yield mentioned, no characterization, no workup or purification mentioned, and of course whereas we can find a photo of a bottle of water for our report no photos of this procedure are available. It's my assumption that the writer did not actually perform the experiment.

ScienceHideout - 24-11-2012 at 07:59

That or he is a pretty sucky chemist! :P

But us chemists like to experiment- We know that you can make acetaldehyde from this procedure, as stated in the very first post in this entire topic.

So, if we give this persons procedure the benefit of the doubt, perhaps we can make it better, and perhaps rewrite a scholarly paper on it!

[Edited on 24-11-2012 by ScienceHideout]

[Edited on 24-11-2012 by ScienceHideout]

chemrox - 24-11-2012 at 19:17

Acetaldehyde is unstable as anything. The best way to store it is as paraldehyde. Paraldehyde is also an effective sedative once used as a "Micky Finn"and for historical (hysterical) reasons it's controlled. I would like a reasonable procedure for converting acetaldhyde to its polymeric form.

ksj_6808 - 25-11-2012 at 20:48

Acetaldehyde is extremely volatile and cannot be stored satisfactorily unless it is refrigerated or sealed in glass ampoules (not just capped), therefore it is necessary to prepare acetaldehyde each time it is needed. There is, however, an easier solution. A quick and easy way to store acetaldehyde is to polymerize it to paraldehyde, which can be handled and stored easily, then depolymerize when you need to use it. Now you can make a larger amount without worry.

To polymerize acetaldehyde for storage, place it in a dry test tube and cautiously add 1 drop of concentrated sulfuric acid per 2 mL of acetaldehyde in the tube. Mix thoroughly, the polymerization will begin to take place. Some gentle warming can hasten the reaction. After some minutes add 3-4 mL of water per 2 mL of acetaldehyde, an insoluble precipitate of paraldehyde will form. As an aside, technically paraldehyde is a controlled substance. It is a sedative and a hypnotic drug useable by prescription only.

To depolymerize paraldehyde back into acetaldehyde, place the paraldehyde into a round-bottom 200-mL Florence flask. Add 4-5 drops of concentrated sulfuric acid for every 20 g (20 mL) of paraldehyde in the flask. Set the flask up for fractional distillation, use glass in the fractionating column. Use a 125-mL Erlenmeyer flask as the receiver; keep it cool by immersing in an ice water (but not salt-ice) bath. Place a loose plug of cotton into the Erlenmeyer flask to help reduce evaporation loss; it must be loose. Care must be taken to prevent the cotton from coming into contact with the distillate. After setting up, heat the flask gently. The temperature of the distillate must not be allowed to rise above 35 °C as it will only repolymerize. The acetaldehyde is now ready for use.

ScienceHideout - 2-12-2012 at 18:44

Do you thing that we could oxidize ethanol with a hypochlorite or a peroxide? I was just thinking that calcium hypochlorite is right up at the top of the oxidizer list near hydrogen peroxide and chromates. If we can oxidize it with a chromate, is it possible that one of the mentioned compounds would work? We can then distill off the acetaldehyde, and polymerize it.

12AX7 - 2-12-2012 at 21:45

Nah, those are much too aggressive. Chromate is milder than either; PCC I believe is preferred further still.


killer_lapin - 24-12-2012 at 14:00

Quote: Originally posted by ScienceHideout  

Check this out:

The only thing that I can't quite figure out is how to capture the acetaldehyde that is formed. Perhaps we can condense it along with acetone, convert it to the trimer, and reproduce te acetaldehyde?

Earlier they mention this technic but they were proposing to oxidise ethanol instead. The difference seems that the acetone is easier to oxidize than ethanol, perhaps the copper catalyst doesn't need to be activated before use.
Quote: Originally posted by Organikum  

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.

For a setup chek here:

blue_vitriol - 28-12-2012 at 08:40

Has anyone tried using MnO2? If that would work it would be extremely convenient, because it can be extracted from batteries.

killer_lapin - 28-12-2012 at 09:56

MnO2 is not powerfull enought. Permanganate could do the job but it's probably to powerfull. But electrogenerated permanganate could work.

Nitro-esteban - 4-6-2013 at 18:50

Quote: Originally posted by Polverone  
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.

I think bleach is composed mainly of hypochlorites which are probably not toxic enough to kill someone.

Salmo - 5-6-2013 at 02:28

what do you think about starting from choline, should be OTC, and than proceed with a hofmann elimination?

[Edited on 5-6-2013 by Salmo]

Nitro-esteban - 5-6-2013 at 11:20

Could potassium permanganate be used to oxidize ethanol or other alcohols? I have plenty of it but it is a carcinogen so I don't want experiment with it unless there is a good chance that it will work.

Dr.Bob - 5-6-2013 at 11:39

Quote: Originally posted by Nitro-esteban  
Could potassium permanganate be used to oxidize ethanol or other alcohols? I have plenty of it but it is a carcinogen so I don't want experiment with it unless there is a good chance that it will work.

Permangenates mixed with alcohols often spontaneously combust, so while you can oxidize alcohols with permangenate, you often will over-oxidize them to acetic acid or CO2, rather than stopping at acetaldehyde, unless you carefully control the conditions. These reactions are normally done dilute, in an inert (to oxidation) solvent to keep the rate slowed down, otherwise they can heat up, accelerating the reaction in an uncontrollable manner.

Even with PCC it can be hard to keep low MW aldehydes from overoxidizing unless you use carefully tuned conditions. But that will usually work if they are dilute, the reaction is not allowed to overheat, and the PCC is added slowly.

AndersHoveland - 29-6-2013 at 03:46

There are several highly selective reagents that can oxidize alcohols to aldehydes, and not any further.
But for just making acetaldehyde, these reagents are probably not practical.

testimento - 3-7-2013 at 21:57

Should acetaldehyde be possible to produce via similar method as formaldehyde: catalytic oxidation of ethanol or acetone with oxygen on copper, silver or palladium catalyst at high temp?

Im gonna run some tests on aldehydation process by making copper pipe spiral installed in heat shield on a propane heat source and distill some methanol, ethanol and acetone through a copper pipe and pumping air with it to induce catalytic reaction.

Products with ethanol and acetone should contain acetaldehyde and ethanoic acic, selectivity varying by the degree of oxidation where faster speeds through catalytic reformer and lower oxygen amounts prefer formation of acetaldehyde and higher oxygen amounts and longer catalyst times prefer the formation of secondary oxidant, ethanoic acid. With methanol the corresponding products should be formaldehyde and formic acid with similar conditions.

The recovery of the products could be done with two receiver flasks, where with acetaldehyde/ethanoic acid the first one serves a receiver for acetic acid, heated at 20C and secondary for acetaldehyde, cooled with ice-salt bath, and with formaldehyde, the primary container holding the formic acid, and secondary containing a water with pipe underneath it to form a formaline solution up to 40%.

[Edited on 4-7-2013 by testimento]

Organikum - 3-7-2013 at 23:02

You did not bother to read the thread as it seems but you seemed to actually do something and so one click might be not to much to enlighten you about temperatures and catalysts for such a process.


edit: wow! I just saw you did not even read the last page, now thats a bit daring my dearest...

and all these posts, will be lost, like tears in the rain...

[Edited on 4-7-2013 by Organikum]

zed - 3-7-2013 at 23:46

"Acetaldehyde is extremely volatile and cannot be stored satisfactorily unless it is refrigerated or sealed in glass ampoules (not just capped), therefore it is necessary to prepare acetaldehyde each time it is needed. There is, however, an easier solution. A quick and easy way to store acetaldehyde is to polymerize it to paraldehyde, which can be handled and stored easily, then depolymerize when you need to use it. Now you can make a larger amount without worry."

Nope, I personally used to own a big glass bottle of it. I don't remember any special problems with it. It is a low boiler, but at normal temperatures, it did not seem to escaped containment, nor did it develop enough vapor pressure to burst the bottle. It would probably be nice to keep it cool in a refrigerator, but it certainly wasn't shipped to me under refrigeration.

plante1999 - 6-7-2013 at 16:46

If I get a good source of ethylene, I might try the Wacker process in an all glass apparatus. If one got Palladium chloride, and ethylene, as well as the ground glass, it is a fairly simple experiment I think. It happens that I have a 5g Aldrich palladium chloride, of which only 0.7g is for my personal use. I remember reading that 0.5% PdCl2 was used, that means I could do a 100ml reaction solution.

I just need ome ethylene and more ground glass, and I would be ready to go.

plante1999 - 7-7-2013 at 16:37

Here is some pictures if people are interested:

<img src="" width="800" />

I'm actually doing a test with non-regenarated dilute palladium chloride solution and propylene, due to my easy access to it, see the mapp pro thread.

<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: reduced image width]

[Edited on 7/8/13 by bfesser]

[Edited on 8-7-2013 by plante1999]

plante1999 - 7-7-2013 at 18:02

For some reason, I have hard time making hydrochloric acid solution of palladium chloride to react with double bonded organic compound, like styrene, propylene, alpha pinene etc... Even when boiling hot. Does anyone got an idea of the reason that makes the experiment not very success full? Apparently the reduction of palladium chloride by double bonded compound was "very easy" and discovered in 1895.

S.C. Wack - 7-7-2013 at 18:09

It's interesting that you're the first person here ever who really wants this. I guess something happened in "I quit", TLDR. A good source of ethylene can be home cooked. 0.5%...references?

...btw...Olefin Oxidations and Related Reactions from Organometallic Reactions v3 1972:

One liter of an aqueous solution containing 17.8 g PdCl2 is charged into a flask connected with a gas burette filled with ethylene and heated up to 50°. After shaking for a few minutes 2.6 liters of ethylene are absorbed and palladium metal is precipitated. Acetaldehyde is isolated by distillation (yield 96%).


An aqueous solution containing 1.78 g PdCl2, 150 g CuCl2.2H2O, and 24 g Cu(OAc)2-H2O per liter is charged in a vertical, heatable glass pipe filled with Raschig rings. At 90-95° a gas mixture of 84% per volume C2H4 and 16% per volume oxygen is passed through the solution with a rate of about 50 liters/hr-liter catalyst. Acetaldehyde is separated from the un- reacted gas by cooling and/or scrubbing with water. The space-time yield under these conditions is 10-15 = g/(l X h) The initial muddy (by basic copper salts) solution becomes dear during the reaction, and a constant oxidation degree is reached. This procedure represents the model for the commercial "one-stage process."

The procedure of the "two-stage process" can be carried out with the same solution if ethylene and air (or oxygen) are introduced alternatively. Ethylene is replaced by air when cuprous chloride begins to precipitate and it is fed again when the solution becomes slurried by copper oxychloride. If the reaction is carried out for a longer time the water removed by the unreacted gas must be compensated for by continuous feeding. After several days of reaction an insoluble precipitate of copper oxalate accumulates. It is formed via chlorinated by-products. In this reaction low amounts of mono-, di- and trichloroacetaldehyde, ethylene chlorohydrin, and others can be observed. Similar side reactions take place with higher olefins.

I wonder if the precipitated Pd is effective for something, since otherwise it just gives 3 grams of acetaldehyde.

plante1999 - 7-7-2013 at 18:38

Thanks, it was a recent crappy chemistry book, I looked in my books, and found a much better reference in Catalysis and chemical processes, page 266, it tells 4g/L as the concentration of palladium chloride.

Much thanks for the reference, I will make the two needed salts for this to try it via the two stage process.

I guess precipitated Pd can be used to hydrogenate thing, or turn to nitrate with HNO3.

plante1999 - 13-7-2013 at 13:10

It works!!!!!


I made a solution of 0.2g of palladium chloride, approx 15g of copper chloride and 1.4g of copper acetate in just enough water to make to make 100 ml solution. It took some time, but everything dissolved.

After this, I made an apparatus with a shortpath, room tempt water filled condenser. The reaction flask had two neck, one with the shorthpath, and one with the gas dispersion tube. A solution of 50ml sulphuric acid and 20ml 70% ethanol was made, and the reaction flask was braugth to boilling. After that, the sulphuric-ethane generator was heated until ethane steadily got out of the flask, after some point a white precipitate formed very rapidly in the flask (copper I chloride), the flask solution turned yellow and a distillate condensed, altough the condenser was not enough efficient. Then, air was passed in, and the solution, slowly all the copper chloride dissolved back to make the green solution back.

Ii is EXTREMLY nice to see the process in action, I must make some change to it, so I can make acetaldehyde out of ethanol!

I will keep everybody updated!

[Edited on 13-7-2013 by plante1999]

plante1999 - 13-7-2013 at 14:55

Ok, so I did another test, with ice cooled water, and it still didn't condensed much acetaldehyde, It did however made lots of HCl gas, I really need more copper acetate buffer in the reaction mixture, I'm pretty sure I also need to add new HCl now. I pretty much made the same smell as when you oppen a bottle of 30% HCl in the summer.

I will need to pass the gas in water I guess.

When the procedure will be successful, I will work on making formaldehyde from Silver and methanol, and make pentaerythriol, for the pyro out there. However, I will probably try to polymerise each to paraformaldehyde and metaldehyde respectively. If anyone want to help me in this project, there is a link in my signature.

here some pictures:

The makeshift apparatus, the white on the reaction flask is due to burning residue:

<img src="" width="800" />

The catalyst solution being used up:

The catalyst solution being regenerated:

The regenerated solution:

<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: reduced image size(s)]

[Edited on 7/14/13 by bfesser]

Using acetone

Jmap labs - 20-7-2013 at 19:36

You can use acetone with a copper oxide catilist. It does make fumes so be careful. Heat copper till red hot then suspend it over some acetone.

Maximus - 21-7-2013 at 01:50

This is just an idea for you guys to evaluate: You all know Elmers's glue is made out of polyvinil acetate polymer and may be some water. The idea would be to dissolve some NaOH in the mixture to hidrolize the ester, maybe add some depolymerization promoter compound and then introduce the mixture into a distillation apparatus, distill the lower fractions, mainly water, and then dry distill the slug to obtain mainly vinyl alcohol and higher fragments of the chain. Of course the vynil alcohol should turn ipso facto in to low boiling acetaldehyde and the lower chain polyvinil alcohol could be added to the next dry distillation. As a bonus one would obtain sodium acetate. How do you guys see this idea? I'm basing it on the thermal depolymerization of styrene and delrin polymers and AFAIK polyvinil alcohol should depolimerize too. Sorry for my english and have a nice day!

BobD1001 - 21-7-2013 at 08:59

Has anyone attempted this synthesis? It seems like a very straightforward and simple way to produce Acetaldehyde. I browsed through the entire thread and didn't see anyone else post this although I may have missed it.

If nobody else has attempted it so far, I can reproduce the experiment, however I only have access to potassium dichromate rather than the sodium salt.

Attachment: Synthesis of Ethanal.pdf (37kB)
This file has been downloaded 1011 times

[Edited on 21-7-2013 by BobD1001]

Organikum - 21-7-2013 at 09:19

An estimated 1.238.876 people have reproduced this synthesis since its invention, for by accident its the standard laboratory procedure for making acetaldehyde and for a long time was a favorite in teaching chemistry.

It is for most here impractical for chrome-salts are hard to come by in most places of the world, up to impossible to legally aquire them as a private person not to talk of bigger amounts.

Thats why other pathways are needed.
For those with the chromium problem at least.


SM2 - 21-7-2013 at 10:15

sry if this already covered. b-alanine in (aq) -0HCL. Bleach or HTH.

papaya - 22-7-2013 at 02:53

Hi, I just happened to try on a very small scale the reaction of 95% ethanol and TCCA, so into few drops of ethanol I put some 200mg of TCCA. I expected a spectacular reaction as TCCA loves to do with things (burst into flames), however i didn't notice even heating but a strong smell appeared I'm not sure what it is, somewhat bitter and a little lacrimatory if you sniff too close(not like chloramine !), I suspect this can be acetaldehyde. As I read there was mentioned about it's synthesis from Ca hypochlorite and ethanol, BUT that was very uncontrollable unlike what I observed with TCCA (though it was small volume and I'm not completely sure on aldehyde).

woelen - 22-7-2013 at 03:16

Do you have a dichromate salt or CrO3? If so, then dissolve some of this in dilute H2SO4 and then add a small quantity of ethanol. Compare that smell with the smell you obtain from TCCA and ethanol.

I am willing to perform your experiment as well and smell the result. I know the smell of acetaldehyde and can certainly tell whether it is that compound or some other stuff. I do not really like the smell of acetaldehyde, but it is not so bad as some people want you to believe.

papaya - 22-7-2013 at 03:24

Hmm, I have some ammonium bichromate if it'll work I can try (isn't that a cognac-like smell at low concs.? ), however I'm afraid that chlorine smell from TCCA admixed with what supposedly is acetaldehyde can make it indistinguishable.. A better test is needed (I have no distillation apparatus also), and be careful if you scale up or do it in glass (who knows), also I want to note my TCCA has significant amounts of boric acid in it, just in case. Thanks!

[Edited on 22-7-2013 by papaya]
EDIT: What is written in wiki

"Ethanol determination

The concentration of ethanol in a sample can be determined by back titration with acidified potassium dichromate. Reacting the sample with an excess of potassium dichromate, all ethanol is oxidized to acetic acid:

CH3CH2OH + 2[O] → CH3COOH + H2O
... "
There must be an error or everything depends on concentrations?

[Edited on 22-7-2013 by papaya]

mayko - 6-9-2013 at 04:53

I remembered a chemistry demonstration where a copper penny is heated until it glows, then suspended in acetone vapors. The hot metal catalyzes the oxidation of acetone, which heats the penny, sustaining the reaction.

The oxidation product appears to depend upon how much oxygen is mixed with the acetone vapor. Oxygenated vapor forms acetaldehyde; anoxic vapor forms ketene.

I wonder if it would work to take a metal pipe and put a copper scrub pad inside, connected to a power supply to give it the initial heating. An aquarium pump passes air through acetone, forming an oxygenated vapor. This passes over the hot copper, then into a condenser.

bfesser - 6-9-2013 at 05:42

I tried this demo a few weeks ago with a bit of copper wire.

<img src="../scipics/_warn.png" /> <em>Beware; one of the products, ethenenone (ketene), is a <a href="" target="_blank">highly toxic gas</a> <img src="../scipics/_wiki.png" />!</em> <img src="../scipics/_warn.png" />

The video that inspired me to try it:
<iframe sandbox width="560" height="315" src="//" frameborder="0" allowfullscreen></iframe>

Jmap labs - 7-9-2013 at 16:49

You could covert acetone to it by a copper oxide catilyst

PHILOU Zrealone - 10-9-2013 at 03:24

Probable viable synthesis via glucose:
1°)fermentation of glucose into lactic acid by lactobacilus

2°)oxydation of lactic acid by conventional oxydisers into pyruvic acid
CH3-CHOH-CO2H -ox-> CH3-CO-CO2H + H2O

3°)thermic decarboxylation at moderate temperature of pyruvic acid into acetaldehyde
CH3-CO-CO2H --> CH3-CH=O + CO2(g)

[Edited on 10-9-2013 by PHILOU Zrealone]

Random - 11-10-2013 at 04:22

Is there a procedure for formation of lactic acid from glucose? Could saccharose be used too?

Lactobacillus can be obtained from yoghurt i guess.

bbartlog - 11-10-2013 at 19:13

Lactic acid can be oxidized directly to acetaldehyde without prior conversion to pyruvic acid, by adding dilute hydrogen peroxide to ammonium lactate solution. At one time this was used as a method for assaying lactic acid in blood (a hundred years ago). Too lazy to dig up the reference but I think Dakin actually published something on this topic.

So far as obtaining lactic acid is concerned, the fermentation is not difficult. I posted something here about it and managed to obtain 1400g of calcium lactate despite being pretty damned sloppy with my process.

[Edited on 12-10-2013 by bbartlog]

Lambda-Eyde - 11-10-2013 at 19:32

Lactobacillus can be bought from White Labs (and maybe Wyeast). It is used for making Belgian-style sour beers (lambic, gueuze among others). Lactic acid can anyways be had cheap from eBay vendors. It is also used in homebrewing for adjusting mash pH.

Formation of Lactate from Sugars

WGTR - 11-10-2013 at 20:12

Quote: Originally posted by Random  
Is there a procedure for formation of lactic acid from glucose? Could saccharose be used too?

Lactobacillus can be obtained from yoghurt i guess.

Process for producing a lactic acid-amine complex
Publication number EP2630114 A1
Publication date Aug 28, 2013

It looks like lactate can be produced directly from the reaction of glucose with barium or calcium hydroxide in a hot water solution.

This is also alluded to in page 335 of:

Victor von Richter's Organic chemistry: or, Chemistry of the carbon compounds, Volume 1, P. Blakiston, 1899.

"Other methods consist in heating grape sugar and cane sugar with water and 2-3 parts barium hydrate to 160C..."

[Edited on 12-10-2013 by WGTR]

Oxidation of lactate to acetaldehyde with H2O2

WGTR - 13-10-2013 at 22:41

Quote: Originally posted by bbartlog  
Lactic acid can be oxidized directly to acetaldehyde without prior conversion to pyruvic acid, by adding dilute hydrogen peroxide to ammonium lactate solution. At one time this was used as a method for assaying lactic acid in blood (a hundred years ago). Too lazy to dig up the reference but I think Dakin actually published something on this topic.
[Edited on 12-10-2013 by bbartlog]

Attached is a useful reference for what you are referring to. Apparently sodium lactate can be oxidized by H2O2 to acetaldehyde when the reaction is done in nitrogen, in the absence of oxygen. If atmospheric oxygen is present, then the acetaldehyde forms peroxides.

Attachment: The Oxidation of Sodium Lactate by Hydrogen Peroxide.pdf (643kB)
This file has been downloaded 873 times

WGTR - 14-10-2013 at 22:00

I decided to try a quick experiment, just to get a feel for what would happen with the lactate approach.

I added enough water to 10.0 g of NaOH to form a 50mL solution, under heavy stirring. In another beaker, 10.0g of dextrose was dissolved in water to form 40mL of solution. Both beakers were heated on a hot plate to 70-80C.

With the NaOH solution under heavy stirring, the dextrose solution was pipetted into the NaOH solution over a period of 30 minutes. As the dextrose was added, the color of the solution progressively went from yellow, to orange, to a dark burnt orange/black as more dextrose was added.

The pH was measured at about 14, and 50% H2SO4 was then added gradually to bring the pH down to about 6. Once the solution was neutral, the color changed from orange/black, to light clear orange. The odor of this solution was not very pleasant at all, and became more noticeable when the solution pH was adjusted to neutral. Looking through some references I realized that I had just performed "Moore's Test", even down to the point of noting the strange odor. (Page 190, Practical Organic and Bio-chemistry By Robert Henry Aders Plimmer; Longmans, Green & Company, 1915)

10mL of this solution was diluted into another beaker to form a 50mL solution, and this was stirred at 30C. 2 mL of 30% H2O2 was added, and the solution was covered and left to stir for several minutes.

I wanted to see if there would be any tell-tale odor of acetaldehyde. If it was there, it was masked by the odd caramel odor already in the solution.

After looking through the reference on the "oxidation of sodium lactate" I listed above, I noticed that they were diluting the lactate to M/50, which I understand to be 1/50 Molar. This is actually very dilute, something that bbartlog alluded to earlier. I think that trying to isolate acetaldehyde from such a diluted solution would cause many frustrations if attempted.

This quick experiment encourages me to go back to working on catalytic dehydrogenation of ethanol instead. I've managed to isolate a small amount of acetaldehyde that way, but I need to work on improving the reactor design to make it more "user friendly".

Taking some ideas from Sabatier's book "Catalysis in Organic Chemistry" and others, I've settled on a single bead-string reactor design. Round copper/magnesium hydroxide beads are threaded onto a copper wire, and the catalyst assembly is inserted into a borosilicate tube. The tube is inserted into an aluminum block (with internal surfaces blackened by FeCl3) to provide even heating, and the block is placed directly on a hot plate set to 300-350C. The hot plate surface and the aluminum block are then covered by firebricks.

The current design leaves the reactor tube in a horizontal configuration, which I don't think is best when trying to reflux the unreacted ethanol. Right now I'm recycling the unreacted ethanol manually after each batch run. The next configuration will be a vertical reaction tube, with a heater built into the aluminum block. This whole assembly will be enclosed in a couple of firebricks, to help retain the heat.

 Pages:  1    3    5