Oxidation of aliphatic aldehydes by benzimidazolium fluorochromate in non aqueous medium - A kinetic and mechanistic study

The oxidation of seven aliphatic aldehydes by benzimidazolium fluorochromate (BIFC) in dimethyl sulphoxide (DMSO) leads to the formation of the corresponding carboxylic acids. The reaction is first order in BIFC. The Michaelis-Menten type kinetics was observed with respect to the aldehyde. The reaction is catalysed by hydrogen ions. The hydrogen-ion dependence has the form: kobs = a + b[H+]. The oxidation of deuterated acetaldehyde, CH3CDO, exhibited a substantial primary kinetic isotope effect (kH/kD = 6.05 at 303 K). Oxidation of acetaldehyde has been studied in eighteen different organic solvents. Various thermodynamic parameters are discussed along with isokinetic temperature. The solvent effect has been analysed using multi parametric equations. A mechanism involving transfer of hydride ion has been suggested. The linear isokinetic correlation implies that all the aldehydes are oxidized by the same mechanism.