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 techniquesat 510 nm, the λmax of [Fe(phen)3]2+ (phen = 1, 10–phenanthroline), the reduced product obtainedin both cases. At ionic strengths, pH ranges and temperature of 0.10–0.60 mol dm-3, 3.25–4.50and 29.0 ± 1.0 oC respectively adopted for this work, first order dependence on the binuclearcomplex 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 ofthe reactions of [Fe2O(phen)4(H2O)2]4+ with N–methylthiourea and N–allylthiourea respectivelyin aqueous phenanthrolinium buffer were both found to be independent of change in pH andvariation in ionic strength. These results were compared with that of the reaction of the titledcomplex with thiourea earlier reported by our team with similar plausible mechanisms proposed.

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