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Acetic anhydride synthesis? Workable?

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limpet chicken:
I had an idea for the synthesis of the commonly used, but hard to obtain reagent acetic anhydride.

KMnO4 oxidises primary alcohols to their respective carboxylic acids, I had the idea of using KMnO4 to oxidise anhydrous, dried ethanol with permanganate, maybe in a solvent forming an easily breakable tertiary azeotrope with AA that could be salted out.

And perhaps just use ethanol or acetic acid as the solvent for the KMnO4, and distill off the acetic anhydride.

Would this work do you think?

This might prove a good replacement for the somewhat tedious and dangerous sandwhich-toaster ketene lamp.

I believe excess permanganate would over oxidise to acetaldehyde though, maybe production of acetaldehyde then mild reduction to the acid anhydride would be better, or use of an alternative oxidant, sodium chlorate, or ammonium nitrate perhaps?

Ideas you smart people out there? :)

Demotivator:
Heating acetic acid to 800C dehydrates it to the anhydride. Could be dangerous as it's very flammable.
or
Convert acetic acid to acetyl chloride. Then rxn with sodium acetate yields acetic anhydride + NaCl.

I don't think using KMnO4 to oxidise anhydrous, dried ethanol  will yield the anhydride, just acetic acid.

limpet chicken:
I don't think the anhydride is formed by simple heating of acetic acid, it forms an azeotrope with water.

movies:
If you did make any acetic anhydride by that method it would more than likely reaction with the ethanol before distilling.  You'd end up with ethyl acetate and acetic acid.

Demotivator:

--- Quote from: limpet chicken on November 28, 2004, 12:39:48 PM ---I don't think the anhydride is formed by simple heating of acetic acid, it forms an azeotrope with water.

--- End quote ---
Right, it wouldn't be simple. It would have to be engineered with a special column.

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