Kinetics and correlation analysis of reactivity in the oxidation of aliphatic primary alcohols by isoquinolinium dichromate in non-aqueous medium

Abstract

Mild oxidation in dimethyl sulfoxide (DMSO) medium by isoquinolinium dichromate (IQDC) of aliphatic primary alcohols produces corresponding carbonyl compounds. A Michaelis-Menten kind kinetics noticed as for alcohols while unit dependency on rate observed as for IQDC. At non-identical temperatures the formation constants and the rates of decomposition of alcohol-IQDC complexes have been evaluated. Thermodynamic parameters and activation parameters for formation of the complex and break down of the complexes have been determined respectively. The oxidation process accelerates with increase in proton concentration. An α-C-H bond fisson in the rate-controlling step suggested by the deuterium isotope effect. For oxidation of ethanol, kH/kD = 5.82 at 293 K, was observed. The oxidation rates have been evaluated in 19 organic solvents and greater role of solvating power of the cation is observed. Depended on the kinetic parameters, solvent effect analysis and the outcome of thermodynamic parameters, a mechanism in which rate-controlling break down of the complex is suggested, to give the resulting product through hydride-ion transfer with a cyclic transition state.