Autocatalyzed oxidation of amino acid, L-Citrulline by diperiodatocuprate(III) complex in aqueous alkaline medium: a kinetics and mechanistic approach

Autocatalysed oxidation of important amino acid, L-Citrulline(L-Cit) by coordination complex, diperiodatocuprate(III) in aqueous alkaline medium at a constant ionic strength of 0.05 mol dm⁻³ was studied spectrophotometrically. Autocatalysis was observed by one of the products formed, i.e., Cu (II). 1:4 stoichiometry (L-Cit:DPC) exhibited between the reaction of L-Cit and DPC in aqueous alkaline medium. The path is of first-order in [DPC], less than unit order in [L-Cit] and independent in [OH^-]. Periodate has a retarding effect on the rate of reaction. Ionic strength has a negligible effect on the reaction rate. The main reaction products were identified by spot tests and spectroscopic analysis. A composite mechanism involving uncatalysed and an autocatalysed reaction path (via free radical) was proposed. The activation parameters for the slow step of the mechanism and also the thermodynamic quantities for different steps of the mechanism were determined and discussed.

Graphic abstract

SYNOPSIS The oxidation of L-Citrulline by diperiodatocuprate(III) complex has been studied. Autocatalysis was observed by one of the products formed, i.e., Cu (II). 1:4 stoichiometry (L-Cit:DPC) exhibited between the reaction of L-Cit and DPC. A composite mechanism involving uncatalysed and an autocatalysed reaction path (via free radical) was proposed.