ORGLIST: dehydroascorbic acid

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From: by way of Joao Aires de Sousa (deutschj$##$essex.UCHSC.edu)
Date: Thu Apr 17 1997 - 19:28:37 EDT


Does anyone know what the acidic proton is in dehydroascorbic acid?
Ascorbic acid, to my understanding, is a lactone, and the acidic proton is
on carbon 3 (hydroxyl), and is where the sodium salt forms.
This proton, and the proton on carbon 2 are both lost when AA is oxidized
to dehydroascorbic acid, (which is also a lactone). Yet, when I make
solutions of 6mM dehydroascorbic acid (DHA from ICN) or 6 mM
ascorbic acid solutions, both have equivalent pH's of approximately 3.5.
I expect some of this is due to hydrolysis of the lactone to the acid
(DKG), but I'm skeptical that it is the only reason.

                                John Deutsch
                                University of Colorado HSC

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