Bach
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Citric acid oxidation
Hi,
what can I expect to happen when mixing citric acid or citrate salts (aqueous solution) with an oxidising agent such as hydrogen peroxide?
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Ritter
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You make malonic acid, CH2(COOH)2. See http://jxb.oxfordjournals.org/cgi/content/abstract/4/2/129
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Formatik
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Conc. HNO3 yields oxalic acid, nitrating acid yields nitrocitric acid. Chlorine under the sun lead into aqueous acid solution gets perchloroacetone
C3Cl6O, but bromine won't react even in sunlight or heat at 100 deg. MnO2 and H2SO4 or aqueous acidified KMnO4 solution oxidizes to CO2 and acetone,
neutral KMnO4 solution gives no acetone, but oxalic acid among other compounds (Beilstein I, 836).
From the same reference, but citrate salts: By action of chlorine into a concentrated aqueous solution of sodium citrate yields perchloroacetone,
CHCl3, and CO2. Bromine into aqueous potassium citrate yields pentabromoacetone.
[Edited on 25-6-2008 by Schockwave]
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not_important
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Interesting, as malonic acid generally oxidises away under similar conditions. Might you be able to post the full paper?
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pantone159
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| Quote: | Originally posted by not_important
Might you be able to post the full paper? |
I think someone posted it somewhere else some months ago, I forget what the topic was. It did not seem to be a useful way to get malonic acid, there
were (IIRC) too many different products, and I think the yield of malonic acid was specified as low (but without numbers.)
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not_important
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It was mentioned months ago in the malonic acid thread, but the full doc wasn't there, nor in the citric acid thread. I'm more interested in what they
did that left enough malonic acid around to be the main product, rather than finding any sort of practical path to malonic acid.
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octave
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I believe all of the other materials were oxidized to malonic acid, then to CO2. So no matter how small an amount of malonic acid remained it was
still the main product. I hope my post made sense 
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pantone159
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| Quote: | Originally posted by not_important
but the full doc wasn't there |
Hmm, I somehow got a copy of this and read it, maybe I went to the dead tree library. I ended up tossing the copy as I decided that process was
either not useful or not fully described or both. I forget the details.
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Ritter
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| Quote: | Originally posted by not_important
Interesting, as malonic acid generally oxidises away under similar conditions. Might you be able to post the full paper? |
Unable, as it requires a subscription to that journal.
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ScienceSquirrel
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The only worthwhile oxidation of citric acid that I have ever heard of is with oleum to yield acetone dicarboxylic acid.
Reactions with a lot of other oxididng agents yield mixtures which are then analysed by HPLC, a good way of producing papers not worthwhile
preparative chemistry!
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theobromacacao
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I've managed to download the aforementioned journal article (free!) so hopefully people can open it! 
Attachment: 129.pdf (746kB)
This file has been downloaded 1580 times
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pantone159
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| Quote: |
Malonic acid on oxidation breaks down to acetic acid and considerable amounts of acetic acid were found in the evaporates of the quinic and citric
oxidation liquids. This breakdown to acetic acid is undoubtedly a contributing cause of the very low final yield of malonic acid
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Thanks for the paper though.
[Edited on 26-6-2008 by pantone159]
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