Mechanism of the oxidation of triphenyl derivatives of P, As, and Sb by peroxodiphosphate
Rate coefficients have been determined for the oxidation of Ph3M (M = P, As, Sb) by potassium peroxodiphosphate. The reaction is found to follow second-order kinetics, first order in each in the oxidant and Ph3M. [H+] has a pronounced accelerating effect on the reaction rate. An interesting dependence of the active species on the nature of the substrate has been observed. The reaction rate is influenced by changing the ionic strength of the medium. Acrylonitrile has no effect on the rate of oxidation. On the basis of the kinetic evidence, a general mechanism involving a biomolecular nucleophilic displacement of the substrate on the peroxo ion has been proposed. The relative rate order is found to be Ph3P > Ph3Sb > Ph3As and an explanation has been offered for the transposition of Ph3Sb and Ph3As.