Kinetics and mechanism of oxidation of fumarate, acrylate, cinnamate, and maleate anions by hexavalent manganese in aqueous alkaline medium

Kinetics of oxidation of fumarate, acrylate, cinnamate, and maleate anions by hexavalent manganese has been studied in aqueous alkaline medium. The order in [oxidant] was unity while that in [substrate] was fractional. The order of reactivity of anions is fumarate → acrylate → cinnamate → maleate. The reactions followed Michaelis–Menten kinetics suggesting the formation of a cyclic intermediate between Mn(VI) and the substrate followed by its disproportionation in a slow step. The equilibrium constant ( K ) for the preequilibrium step and the rate constant ( k ) for the slow disproportionation step have been calculated from the intercept and the slope values of the linear plot of 1/ k obs versus 1/[substrate]. Activation parameters are also presented and discussed. A convenient iodometric method is reported for the estimation of Mn(VI).