Manganese(III) Oxidation of Alanine in Aqueous Ethanoic Acid Medium: A Kinetic and Mechanistic Study.

A stock solution of manganese(III) acetate in aqueous acetic acid has been prepared using a standard electrochemical method. The nature of the oxidizing species present in manganese(III) solutions has been characterized by spectrophotometric and redox potential measurements. Kinetics of oxidation of DL-alanine (Ala) by manganese(III) in aqueous acetic acid solution at 313 K have been investigated. The experimental rate law is: rate = k′[Mn(III)]0.5[Ala]0.9 [OAc−]y0.5/[H+]0.5, where each species shows a fractional order. Effects of varying ionic strength, solvent composition, and the added ions such as fluoride, chloride, and perchlorate have been investigated. Activation parameters have been evaluated using Arrhenius and Eyring plots. A mechanism consistent with the observed kinetic data has been proposed and discussed. A suitable rate law has been derived based on the mechanism. [ABSTRACT FROM PUBLISHER]