Structure-reactivity relation in the oxidation of some aliphatic aldehydes by Tripropylammonium chlorochromate

Abstract

The oxidation of six aliphatic aldehydes by tripropylammonium chlorochromate (TPACC) in dimethyl sulfoxide (DMSO) leads to the formation of corresponding carboxylic acids. The reaction is of first order each in TPACC. A Michaelis-Menten type of kinetics is observed with respect to the aldehydes. The reaction is catalysed by hydrogen ions. The hydrogen-ion dependence has the form: kobs = a + b[H+]. The oxidation of deuteriated acetaldehyde MeCDO exhibited a substantial primary kinetic isotope effect (kH/kD = 5.75 at 298 K). The oxidation of acetaldehyde has been studied in nineteen different organic solvents. The solvent effect has been analysed using Taft's and Swain's multiparametric equations. The rate constants correlate well with Taft’s * values, reaction constants being negative. A mechanism involving transfer of hydride ion has been suggested.