OXIDATION REACTION OF L-ASCORBIC ACID BY DICYANOBIS(1,10-PHENANTHROLINE)IRON(III) IN DIMETHYL SULFOXIDE AT ELEVATED PRESSURES - EVIDENCE FOR ADIABATIC ELECTRON TRANSFER

摘要

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. [References: 34]