Oxidation reaction of l-ascorbic acid by dicyanobis(1,10-phenanthroline)iron(III) in dimethyl sulfoxide at elevated pressures: evidence for adiabatic electron transfer

Abstract Kinetic measurements of the oxidation reaction of l -ascorbic acid by dicyanobis(1,10-phenanthroline)iron(III) were carried out at elevated pressures. The activation volume corresponding to the one-electron oxidation process of l -ascorbic acid was −0.5±1.3 cm 3 mol −1 . The reaction mechanism was analyzed by using the volume cross relation based on the Stranks–Hush–Marcus theory. Estimation of the reaction volume of the ascorbic acid radical/ascorbic acid couple revealed that the oxidation reaction of ascorbic acid proceeds through a simple adiabatic process in DMSO, while an electron transfer followed by a rapid ring-closure reaction within the ascorbic acid radical was suggested for the reactions in aqueous solution.