Kinetics and Mechanism of the Reaction of Malachite Green and Dithionite Ion
S. O. Idris *
Department of Chemistry, Ahmadu Bello University, Zaria, Nigeria
A. Tanimu
Department of Chemistry, Ahmadu Bello University, Zaria, Nigeria
J. F. Iyun
Department of Chemistry, Ahmadu Bello University, Zaria, Nigeria
Y. Mohammed
Department of Chemistry, Nasarawa State University, Keffi, Nigeria
*Author to whom correspondence should be addressed.
Abstract
The kinetics of the oxidation of malachite green, MG+, by dithionite ions, S2O42- have been studied spectrophotometrically in an aqueous acid free medium. The investigation was carried out under pseudo- first order conditions of an excess of dithionite concentration. Reaction conditions were ionic strength of reaction medium, µ = 0.1 mol dm–3, λmax = 620nm and T = 25.5±0.5°C. The stoichiometry of the reaction, determined by spectrophotometric titration, was 1:1. Reaction rates increased with increase in µ and dielectric constant (D) of reaction medium. Added ions catalysis of the reaction and the result of the Michaelis - Menten analysis suggest that the reaction proceeded through the outersphere pathway. A plausible mechanism is proposed.
Keywords: Kinetics, mechanism, outersphere, dithionite ion, malachite green