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 (HClO₄) medium at I = 1.00moldm^-3(NaClO₄) 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-] = k₂[Co(Ox)₃^3-][H₂Q]. Where k₂ = k_a[H⁺]. The experimental results are in favour of the outer-sphere mechanism.

Nigerian Journal of Chemical Research Vol. 9, 2004: 35-39