Kinetics of oxidation of phosphinic, phenylphosphinic and phosphorous acids by bromamine-B in aqueous perchloric medium

Abstract

The oxidation of phosphinic, phenylphosphinic and phosphorous acids by sodium N-bromoben-zenesulphonamide (BAB) in perchloric acid solution, results in the formation of corresponding phosphorous acids of higher valence state. The reaction is first order in [BAB], [oxyacid] and [H⁺]. Oxidation of deuteriated phosphinic and phosphorous acids shows the presence of a substantial primary kinetic isotope effect. The reaction fails to induce polymerization of acrylonitrile. Added benzenesulphonamide has no effect on the reaction rate. (PhSO₂NH₂Br)⁺ has been postulated as the reactive oxidizing species. It has been shown that the inactive tautomer of the phosphorous oxyacids, RHP(O)OH, participates in the oxidation process. A rate-determining step involving transfer of a hydride ion from the P - H bond to the oxidant has been proposed.