JimmyBC
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Diacetyl
Hi,
There is a lot of info on the forum here and the web about synthesis of sodium acetate from Vinergar and a sodium base, usually Na2CO3. I have done
this once and got a brown solution which smelled buttery. This was Diacetyl, an artificial butter flavoring.
How can I make diacetyl more effectively and how would I go about purifying it?
BP: 88 Celcius and Freezes at -3 Celcius.
Baking Soda and Vinegar seems easy enough. Will making the solutuion slightly basic or acidic make formation of diacetyl more favorable? Basically, iS
there a more efficient/better way of making it?
Jimmy
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not_important
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I suspect that it was there as an impurity in the vinigar, formed during fermentation. Doesn't take much diacetyl for it to be smelled.
It's normally made from methyl ethyl ketone, one method is oxidation using air or oxygen and a a heated zeolite catalyst such as VS-1
[Edited on 23-9-2006 by not_important]
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JimmyBC
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So its not really necessary to neutralize the vinegar, can I can just boil down vinegar and be just as effective in getting diacetyl?
JimmyBC
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Nicodem
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You don't get it. You don't get no 2,3-butanedione ("diacetyl") by acetic acid neutralization or boiling down. From where did you even got such an
idea in the first place?
If you need 2,3-butanedione, it can be prepared by nitrosating methyl ethyl ketone and then hydrolyzing the so formed oxime.
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JimmyBC
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Nicoderm, what are you talking about! Do some searching under "sodium acetate."
Numerous poeple here have reported smells when neutralizing vinegar with NaHCO3. They are either Diacetyl or Acetaldehyde depending on the situation.
Unionized said: "A good part of the smell of neutralised vinegar is butane dione (AKA biacetyl, AKA diacetyl)"
Cyprus said: "I noticed a fruity smell when doing this reaction that wasn't sodium bicarbonate or vinegar. Does AA smell fruity?"
Obviously I didn't pull this out of my A$$.
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Nicodem
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2,3- butanedione is a byproduct from malic acid in the fermentation process (from vine, apples or whatever is used to make vinegar). Obviously, it
does not form during the neutralization. How could it? There is no mechanistical allowance for such a reaction. Absolutely nothing but deprotonation
happens to acetic acid in its reaction with bases.
See the first sentence in http://en.wikipedia.org/wiki/Diacetyl
I hope this will teach you not to jump to absurd conclusions just from reading someone's comment about a smell during some experiment. Trust me, there
is no fruity smell evolved when you neutralize reagent grade acetic acid.
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unionised
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The biacetyl is present in the vinegar to begin with but you can't smell it because of the acetic acid (which smells srongly enough to cover up the
biacetyl).
Adding base removes the acetic acid so the odour of biacetyl becomes aparent.
I don't know what the total quantity of biaetyl is but I doubt it's as much as 0.1%
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12AX7
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I've got alcohol and acetic acid vapors around two crystallizing things, it smells kind of fruity, neither acid not alcoholic, in combination, at
least at whatever dilution.
But yeah, you aren't going to get diacetyl from acetic acid per se...
Tim
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