ALKALI-METAL ION CATALYSIS OF THE OXIDATION OF L-ASCORBIC-ACID BY HEXACYANOFERRATE(III) IN STRONGLY ACIDIC MEDIA

The kinetics of the oxidation Of L-ascorbic acid by hexacyanoferrate(III) ions have been investigated in strongly acidic media over a wide range of acidity. Two different mechanisms involving the monoascorbate anion, AH-, the neutral molecule of ascorbic acid AH-2, and the protonated species AH-3+, as well as the hexacyanoferrate(III) ion Fe(CN)63-, and the monoprotonated form HFe(CN)62- are suggested. Kinetic evidence for a specific catalytic effect by binding of alkali-metal ions to oxidant is reported. The derived rate equations are in good agreement with the experimental observations.