Kinetics and mechanisms of redox reactions in aqueous solution. Part 9. Permanganate oxidation of phosphorous acid in perchlorate solution

Abstract

The reaction between phosphorous acid and permanganate exhibits a first-order dependence both on [Mn^VII] and [H₃PO₃] and the dependence of k_obs. on [H⁺] is of the form (i) at constant ionic strength; k_obs.=a+b[H⁺](i)k_obs. is independent of ionic strength. The most probable mechanism in which the ‘inactive’ form of phosphorous acid, H–PO(OH)₂, is the reactive species is discussed and the values of the rate-limiting constants together with their associated thermodynamic parameters are reported. The duality of H⁺ catalysis is also discussed in an alternative mechanism.