Kinetics and mechanism of oxidation of oxovanadium(IV) and its amino polycarboxylate and heterocyclic ligand complexes by peroxomonosulphate in orthophosphoric acid medium

Abstract

Kinetics of oxidation of aquo oxovanadium(IV) and its complexes with ethylenediamine tetraacetate (edta), N-(2-hydroxy ethyl) ethylenediamine triacetate (hedta), 1,10-phenanthroline (phen) and 2,2'-bipyridyl (bipy) by peroxomonosulphate (PMS) in orthophosphoric acid {[H⁺]=(2.0-12.0) x 10^-2 mol dm^-3} medium has been investigated under pseudo-first order conditions using a stopped flow spectrophotometer by monitoring the decay of the substrate at 585 nm. The relative reactivities of these complexes have been found to be in the order VO<img src='http://www.niscair.res.in/jinfo/equation71.gif' border=0> > [VO(bipy)₂]²⁺> [VO(edta)^2- > [VO(phen)₂]²⁺. In the oxidation of [VO(edta)]^2-, both the protonated and unprotonated species of the complex compete for the oxidant.