Kinetics and mechanism of the oxidation of secondary alcohols by tetrabutylammonium tribromide

Abstract

Oxidation of several secondary alcohols by tetrabutylammonium tribromide (TBATB) in aqueous acetic acid leads to the formation of corresponding ketones. The reaction is first order with respect to TBATB and the alcohols. The reaction failed to induce polymerization of acrylonitrile. There is no effect of tetrabutylammonium chloride on the reaction rate. The proposed reactive oxidizing species is tribromide ion. The oxidation of benzhydrol-α-d (PhCDOHPh) exhibited a substantial primary kinetic isotope effect (k H /k D = 5.15 at 298 K). The effect of solvent composition indicates that the rate increases with an increase in polarity of the solvent. The reaction is susceptible to both polar and steric effects of the substituents. A mechanism involving transfer of a hydride ion in the rate-determining step has been proposed.