Kinetics and Mechanism of the Oxidation of Formic and Oxalic Acids by Imidazolium Fluorochromate

Abstract

Kinetics and mechanism of oxidation of formic acid and oxalic acid by imidazolium fluorochromate have been studied in dimethyl sulphoxide. The main product of oxidation is carbon dioxide. The reaction is first order with respect to imidazolium fluorochromate. Michaelis- Menten type of kinetics were observed with respect to the reductants. The reaction is acidcatalyzed and the acid dependence has the form: k_obs = a + b [H⁺]. The oxidation of a- deuterioformic acid exhibits a substantial primary kinetic isotope effect (k_H/k_D = 5.30 at 298 K). The reaction has been studied in 19 different organic solvents and the solvent effect has been analyzed using Taft's and Swain's multiparametric equations. The temperature dependence of the kinetic isotope effect indicates the presence of a symmetrical cyclic transition state in the rate-determining step. Suitable mechanisms have been proposed.