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 AH2, and the protonated species AH+3, as well as the hexacyanoferrate(III) ion Fe(CN)3–6, and the monoprotonated form HFe(CN)2–6 are suggested. Kinetic evidence for a specific catalytic effct by binding of alkali-metal ions to oxidant is reported. The derived rate equations are in good agreement with the experimental observations.