Oxidation of threonine by the analytical reagent diperiodatocuprate(III) – An autocatalysed reaction

The kinetics of Cu(II) autocatalysed oxidation of threonine by well-recognized analytical reagent diperiodatocuprate(III) in aqueous alkaline medium at a constant ionic strength of 0.5 mol dm−3 was studied spectrophotometrically. The reaction between diperiodatocuprate(III) and threonine in alkaline medium exhibits 2:1 stoichiometry (DPC: threonine). The reaction is of first order in each [DPC] and [threonine] and less than unit order in [alkali]. Periodate has retarding effect on the rate of reaction. Ionic strength has negligible effect on the reaction. Increase in dielectric constant of the medium with decrease in the rate of the reaction was observed. The product, Cu(II), catalyses the reaction with a fractional order. The main products were identified by spot test and I.R. A composite mechanism involving the monoperiodatocuptrate(III) (MPC) as the reactive species of the oxidant in uncatalysed and autocatalysed reaction has been proposed. Activation parameters and the reaction constants involved in the different steps of the mechanisms are calculated.