Kinetics and mechanism of oxidation of aromatic aldehydes by vanadium(V) in perchloric acid medium

Abstract

The oxidation kinetics of benzaldehyde and its substituted derivatives by vanadium(V) have been studied in perchloric acid medium. The reaction is first order in both [vanadium(V)] and [H⁺] whereas the order with respect to [substrate] is less than unity. The kinetic and spectrophotometric results indicate the formation of an intermediate 1 : 1 complex between the reactive vanadium(V) species and hydrated benzaldehyde prior to electron transfer. Thermodynamic parameters associated with the intermediate complex and activation parameters for the slow step have been evaluated. The reaction is found to have a significant deuterium isotope effect. A mechanism consistent with the experimental observations is proposed.