Oxidation of secondary alcohols by sodium N-chlorobenzenesulphonamide in aqueous solution. A kinetic study

Abstract

The kinetics of oxidation of five secondary alcohols by sodium N-chlorobenzenesulphonamide (chloramine-B) has been studied in acid medium at 40°C. The reaction is first order with respect to the oxidant and alcohol and fractional order in [H+]. The influence of added halide ions and of reaction product and the effects of varying ionic strength and dielectric constant of the medium have also been studied. The solvent isotope effects k’(H2O)/k’(D2O) were determined. The rates were studied at four different temperatures and the activation parameters were evaluated. Attempts have been made to arrive at a linear free energy relation through the Taft treatment. An isokinetic relation is observed with β = 248 K, indicating the entropy of activation as the rate controlling factor. Protonated chloramine-T (monochloramine-T) has been postulated as the reactive oxidizing species, the main product of oxidation being the corresponding ketone. A mechanism involving the interaction of protonated haloamine species and the alcohol in a rate limiting step has been proposed.