Kinetics and mechanism of the oxidation of the calcium complex of ethylenediaminetetra-acetic acid by perbenzoic acids

Abstract

The rate of oxidation of ethylenediaminetetra-acetic acid (EDTA) by perbenzoic acids in aqueous acetate buffers is retarded by added calcium ions. The oxidation of CaEDTA^2– proceeds via parallel pathways involving dissociation and subsequent oxidation of the ligand and direct nucleophilic attack of the nitrogen atom of the complex on the outer peroxidic oxygen of the peracid respectively. The mechanism of the latter pathway is discussed. An application of the Ca–EDTA system as a reservoir of EDTA for the inhibition of interfering trace-metal-ion catalysed reactions of peracids is suggested.