Kinetics of the oxidation of organic sulphides by pyridinium fluorochromate

Abstract

The kinetics of the oxidation of a number of monosubstituted aryl methyl, alkyl phenyl, dialkyl, and diphenyl sulphides by pyridinium fluorochromate (PFC) to yield the corresponding sulphoxides have been studied. The reaction is first order with respect to the sulphide and PFC. The reaction exhibited negative polar reaction constants and a small degree of steric hindrance. The analysis of the rates in 19 different solvents indicated an electrophilic attack of a PFC oxygen on the sulphide yielding a polar transition state. Moderate anchimeric assistance was observed in the oxidation of o-CO₂H- and o-CO₂Me-substituted phenyl methyl sulphides. A mechanism involving a one-step electrophilic oxygen transfer from PFC to the sulphide and a polar transition state has been proposed.