Polarographic Investigations of Vitamin C. II. On the Reduction Waves of Some Conjugated Tricarbonyl Compounds as Related Compounds of Dehydro-l-ascorbic Acid

Abstract

Abstract Alloxan, dehydro-reductic acid and mesoxalaldehyde show reduction waves which are similar to that of dehydro-l-ascorbic acid. The half-wave potentials of alloxan, dehydro-reductic acid, dehydro-l-ascorbic acid and mesoxalaldehyde in pH 3.5 are −0.05, −0.27, −0.42 and −0.35 V. (vs. N.C.E.), respectively. Of these four substances, the lower the height of the reduction wave, the greater both the shift of the half-wave potential of the anodic wave of the corresponding reduced form from the standard oxidation-reduction potential of the system and the temperature coefficient of the height of the reduction wave. Inactive forms of these substances at the electrode reaction may be the hydrated ones as proposed in the case of dehydro-l-ascorbic acid. Alloxan has been proved to be polarographically reversible by the controlled potential electrolysis and the half-wave potential of the reduction wave coincides with that of the oxidation wave of dialuric acid, while no such observations have been made with the other three.