Sciencemadness Discussion Board

Various routes to acetaldehyde

aromaticfanatic - 21-11-2020 at 22:39

I am aware of the big thread on acetaldehyde, but has anyone tried the following:

Dry distillation of calcium formate and calcium acetate.

Hydration of acetylene.

I am interested in the latter but the major drawback is that I do not want to use mercury salts. I am not aware of any substitutes so far. Oh and to make it better, it seems that methylmercury is made as a by product as well. Screw that.

Typically dichromates are used with ethanol and sulfuric acid to make acetaldehyde but has anyone tried it with KMnO4? It is said that primary and secondary alcohols tend to be oxidized to the carboxylic acid and that the aldehydes are oxidized by the KMnO4 as well. So I suspect the yield would be very low. Is it possible to inhibit aldehyde oxidation?

[Edited on 22-11-2020 by aromaticfanatic]

[Edited on 22-11-2020 by aromaticfanatic]

[Edited on 22-11-2020 by aromaticfanatic]

mackolol - 22-11-2020 at 03:50

I really doubt that it can be done with KMnO4, it's too strong oxidant. I don't really know how would the inhibition of further oxidation look like. Maybe it can be done with MnO2, but surely not with KMnO4.
And by the way, secondary alcohols cannot be oxidised to carboxylic acids. Farthest you can go is ketone.

karlos³ - 22-11-2020 at 08:05

You can probably do a sommelet reaction on ethyl iodide with hexamine, and then hydrolyse and distill the acetaldehyde off directly from the reaction.
I wanted to try this, but never got around to do so.

KMnO4 will produce only traces at most.

Corrosive Joeseph - 22-11-2020 at 08:58

I don't know why the OP is so special that he couldn't just post in the 19 page, 18 year old acetaldehyde sticky.
Anyway, I always liked the look of this one.
Quote:


If you treat aq. solution of tartaric acid with MnO2 in the heat, at 35°C CO2-evolution begins. At the same time acetaldehyde forms.



https://www.sciencemadness.org/whisper/viewthread.php?tid=55...

Check out all my posts on that page.



/CJ

aromaticfanatic - 27-11-2020 at 10:15

Quote: Originally posted by Corrosive Joeseph  
I don't know why the OP is so special that he couldn't just post in the 19 page, 18 year old acetaldehyde sticky.
Anyway, I always liked the look of this one.

Quote:


If you treat aq. solution of tartaric acid with MnO2 in the heat, at 35°C CO2-evolution begins. At the same time acetaldehyde forms.



https://www.sciencemadness.org/whisper/viewthread.php?tid=55...

Check out all my posts on that page.



/CJ


Thanks I've never heard of that route.

I looked through that thread but I didn't know if I should post there since it didn't seem the most active and it's very lengthy. I figured these different synthesis would be better fit in a new thread. That's just me though.

EverythingAl2O3 - 2-12-2020 at 15:54

Why bother with stuff as annoying as Acetylene or dangerous as chromium and mercury? Isn't it right that OH-C=C leads to O=C-C? So just dehydrate ethylene glycol, get your enol and let it rapidly tautomerize into acetaldehyde which at the temperatures that it needs to be heated to dehydrate will boil it off.
Quote:

I am aware of the big thread on acetaldehyde, but has anyone tried the following:

Dry distillation of calcium formate and calcium acetate.

Hydration of acetylene.

I am interested in the latter but the major drawback is that I do not want to use mercury salts. I am not aware of any substitutes so far. Oh and to make it better, it seems that methylmercury is made as a by product as well. Screw that.

Typically dichromates are used with ethanol and sulfuric acid to make acetaldehyde but has anyone tried it with KMnO4? It is said that primary and secondary alcohols tend to be oxidized to the carboxylic acid and that the aldehydes are oxidized by the KMnO4 as well. So I suspect the yield would be very low. Is it possible to inhibit aldehyde oxidation?