Abstract
The kinetic results of the oxidation of methionine by MnO4- in aqueous medium are presented. Upon mixing aqueous solutions of permanganate and methionine, a readily distinguishable brown colour appears. Under pseudo-first order conditions ([methionine]>[MnO4-]), the formation and decomposition of brown colour was very fast. Experiments have been made to confirm the nature of brown colour formed during the reduction of MnO4- by methionine. The kinetics of both the stages (formation and decomposition of colloidal MnO2) was investigated spectrophotometrically. Second-and pseudo-first-order conditions were used to determine the reaction rate for the formation and decomposition of colloidal MnO2, respectively. The changes observed in the direction of the rate constant -[H+] profile correspond to the hydrolysis of the colloidal MnO2. The addition of sodium fluoride has composite effect (catalytic and inhibition). The proposed mechanism and the derived rate law are consistent with the observed kinetics.