Kinetics and Mechanism of Oxidation of Bromate by Diperiodatonickelate(IV) in Aqueous Alkaline Medium--A Simple Method for Formation of Perbromate

Abstract

The kinetics of oxidation of bromate by diperiodatonickelate(IV) (DPN) in alkaline medium at a constant ionic strength has been studied spectrophotometrically. The reaction between DPN and bromate in alkaline medium exhibits 1:1 stoichiometry (DPN:bromate). The reaction shows first order dependence on [DPN] and zero order dependence in [bromate] and less than unit order dependence in alkali concentrations. Periodate has a retarding effect on the rate of reaction. Reaction rate increases with increase in ionic strength and decrease in solvent polarity of the medium. Initial addition of reaction products did not affect the rate significantly. A mechanism involving the monoperiodatonickelate(IV) (MPN) as the reactive species of the oxidant has been proposed. The reaction constants involved in the mechanism are evaluated. The activation parameters were computed with respect to the slow step of the mechanism.