Mechanistic Investigations on the Oxidation of L-valine by Ag(III) Periodate Complex in Alkali Media: a Kinetic Approach

The oxidation of an amino acid, L-valine (L-val) by diperiodatoargentate(III) (DPA) in alkaline medium at a constant ionic strength of 0.006 mol dm–3 was studied spectrophotometrically. The reaction between DPA and L-val in alkaline medium exhibits 1:1 stoichiometry (L-val:DPA). Intervention of free radicals was observed in the reaction. Based on the observed orders and experimental evidences, a mechanism involving the protonated diperiodatoargentate(III) (DPA) as the reactive species of oxidant has been proposed. The products were identified by spot test and characterized by spectral studies. The reaction constants involved in the different steps of the mechanism were calculated. The activation parameters with respect to slow step of the mechanism were computed and discussed. The thermodynamic quantities were determined for different equilibrium steps. Isokinetic temperature was also calculated and found to be 188.9 K.