Kinetics and Mechanism of the Oxidation of Dl-Methionine by Benzimidazolium Dichromate

Abstract

The oxidation of DL-methionine (MT) by benzimidazolium dichromate (BIDC), in dimethyl sulfoxide, leads to the formation of the corresponding sulfoxide. The reaction is first order with respect to BIDC. Michaelis - Menten type kinetics were observed with respect to MT. The reaction is catalysed by hydrogen ions and the dependence is of the form kobs = k‘[H+]. The rate of oxidation of MT was determined in 19 organic solvents. An analysis of the solvent effect by solvatochromic equations indicated that though both the anion- and cation-solvating powers of the solvent contribute to the observed solvent effect, the role of cation-solvation is much the major. A suitable mechanism has been proposed.