Kinetic and mechanistic study of oxidation of L-aspartic acid by diperiodatocuprate(III) in aqueous alkaline medium

The kinetics of oxidation of L-aspartic acid (L-ASPA) by diperiodatocuprate(III) (DPC) in aqueous alkaline medium at a constant ionic strength of 0.5 mol dm(-3) was studied spectrophotometrically. The reaction between diperiodatocuprate(III) and L-aspartic acid in alkaline medium exhibits 2:1 stoichiometry (DPC: L-ASPA). The reaction is of first order in [DPC], less than unit order in [L-ASPA] and [alkali]. Periodate has a retarding effect on the rate of the reaction. Dielectric constant of the medium has no effect on the rate of reaction. Effect of added products and ionic strength of the reaction medium has been investigated. A mechanism involving the monoperiodatocuptrate(III) (MPC) as the reactive species of the oxidant has been proposed. In complex equilibrium step L-ASPA binds to MPC species to form a complex (C). Then this complex (C) decomposes in a slow step to form an intermediate free radical species, which reacts with another molecule of MPC species in a Fast step to yield the products. The activation parameters with respect to slow step of the reaction are computed and discussed.