Palladium(II)-Catalyzed Oxidation of α-Hydroxy Acids with Sodium N-Chlorobenzenesulfonamide in Perchloric Acid Solution: A Kinetic and Mechanistic Study

Abstract

Kinetics of oxidation of glycolic acid (GA), lactic acid (LA) and 2-hydroxybutanoic acid (BA) with Chloramines B (CAB) catalyzed by Pd(II) in a HClO4 solution has been studied at 30 °C. The reaction rate shows first-order dependence each on [CAB], [hydroxy acid] and [Pd(II)] and a fractional-order dependence on [H+]. Additions of chloride ions, perchlorate ions and the reduction product of CAB, benzenesulfonamide (BSA), have no effect on the reaction rate. Variations of ionic strength and dielectric permittivity of the medium have no effect on the rate. Activation parameters have been evaluated. A mechanism consistent with kinetic data is proposed. A Taft linear free-energy relationship is observed for the reaction with ρ* = -3.593, indicating an increase in the rate with the presence of electron-donating substituents. An isokinetic relationship is observed with β = 376 K, indicating the effect of enthalpy factors on the rate.