Alkali-metal ion catalysis of the oxidation of L-ascorbic acid by hexacyanoferrate(III) in strongly acidic media

Abstract

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.