Conversion of Manganate(VI) to Manganate(VII) By N -bromosuccinimide in Aqueous Alkaline Medium: A Kinetic and Mechanistic Approach

Abstract

N -bromosuccinimide oxidation of manganate(VI) was studied spectrophotometrically. The reaction showed first order kinetics in [ MnO 4 2 m ] and an apparent less than unit order dependence in [NBS] and rate of reaction decreases with increase in [alkali]. Initial addition of products had no significant effect on the rate of the reaction. The effect of ionic strength and dielectric constant of the reaction medium have been investigated. The results suggest that the reaction proceeds via formation of a complex between active species of oxidant and MnO 4 2 m , which subsequently decomposes in a rate determining step followed by a fast step to yield the products. A mechanism involving the HOBr as the reactive species of the oxidant has been proposed. The reaction constants involved in the mechanism have been computed. There is a good agreement between the observed and calculated rate constants under different experimental conditions. The activation parameters were calculated with respect to the slow step of t...