Oxidation of L-leucine by alkaline diperiodatoargentate(III) deamination and decarboxylation: A kinetic and mechanistic study

The oxidation of L-Leucine by alkaline diperiodatoargentate(III) (DPA) at 298 K and a constant ionic strength of 1.0 mol dm^-3 was studied spectrophotometrically. The oxidation products are pentanoic acid and Ag (I). The stoichiometry is [L-Leucine]:[DPA] = 1:2. The reaction is of first order in [DPA] and has less than unit order in both [L-Leucine] and [alkali] and a retarding effect in [IO₄^-]. The oxidation reaction in alkaline medium has been shown to proceed via a L-Leucine-DPA complex, which further reacts with one molecule of DPA in a rate-determining step followed by other fast steps to give the products. The main products were identified by spot test and IR. The reaction constants involved in the different steps of the mechanism are calculated. The activation parameters with respect to the slow step of the mechanism are computed and discussed, and thermodynamic quantities are also determined. The probable active species of oxidation have been identified.