Kinetics and mechanism of the redox reaction between catechol and trisoxalatocobaltate (III) ion in aqueous acid medium

Abstract

The kinetics of the reduction of [Co(Ox) 3 ] 3- with catechol has been studied in aqueous acid (HClO 4 ) medium at I = 1.00moldm -3 (NaClO 4 ) and T=26.3±0.1°C. Two moles of oxidant were consumed by one mole of reductant. The reaction is second order overall, first order in both oxidant and reductant and shows a first order direct acid dependence. Polymerisation test suggested the presence of free radicals as intermediates in the reaction. The kinetic data are consistent with the following equation: -d/2dt[Co(Ox) 3 3- ] = k 2 [Co(Ox) 3 3- ][H 2 Q]. Where k 2 = k a [H + ]. The experimental results are in favour of the outer-sphere mechanism. Nigerian Journal of Chemical Research Vol. 9, 2004: 35-39