Kinetics and mechanism of the oxidation of formic and oxalic acids by quinolinium fluorochromate

Kinetics and mechanism of oxidation of formic and oxalic acids by quinolinium fluorochromate (QFC) have been studied in dimethylsulphoxide. The main product of oxidation is carbon dioxide. The reaction is first-order with respect to QFC. Michaelis–Menten type of kinetics were observed with respect to the reductants. The reaction is acid-catalysed and the acid dependence has the form: kobs = a + b[H+]. The oxidation of a-deuterioformic acid exhibits a substantial primary kinetic isotope effect (kH/kD = 6,1 at 303 K). The reaction has been studied in nineteen different organic solvents and the solvent effect has been analysed 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.