Abstract

The kinetics of the oxidation of N–methylthiourea and N–allylthiourea respectively by µ–oxo–tetrakis(1, 10–phenanthroline)diiron(III) complex ion ([Fe2O(phen)4(H2O)2]4+) in aqueous phen–phenH+ buffer solution have been studied spectrophotometrically using conventional techniques at 510 nm, the λmax of [Fe(phen)3]2+ (phen = 1, 10–phenanthroline), the reduced product obtained in both cases. At ionic strengths, pH ranges and temperature of 0.10–0.60 mol dm-3, 3.25–4.50 and 29.0 ± 1.0 oC respectively adopted for this work, first order dependence on the binuclear complex was observed for the two systems. First order dependence was also observed for N–allylthiourea in the [Fe2O(phen)4(H2O)2]4+–N–allylthiourea system while for the [Fe2O(phen)4(H2O)2]4+–N–methylthiourea system, mixed first and zero order dependence on N–methylthiourea was found. Keeping the concentrations of all the reactants constants, the rates of the reactions of [Fe2O(phen)4(H2O)2]4+ with N–methylthiourea and N–allylthiourea respectively in aqueous phenanthrolinium buffer were both found to be independent of change in pH and variation in ionic strength. These results were compared with that of the reaction of the titled complex with thiourea earlier reported by our team with similar plausible mechanisms proposed.

Key words: kinetics, mechanism, N–allylthiourea, N–methylthiourea, oxidation, phenanthrolinium buffer,