OXIDATION OF SOME ALIPHATIC ALDEHYDES BY IMIDAZOLIUM FLUOROCHROMATE. A KINETIC AND MECHANISTIC STUDY

The oxidation of 6 aliphatic aldehydes by imidazolium fluorochromate (IFC) in dimethyl sulphoxide (DMSO) leads to the formation of corresponding carboxylic acids. The reaction is first order each in IFC. 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: k(obs) = a + b[H+]. The oxidation of deuteriated acetaldehyde, MeCDO, exhibited a substantial primary kinetic isotope effect (k(H)/k(D) = 5.78 at 298 K). The oxidation of acetaldehyde has been studied in 19 different organic solvents. The solvent effect has been analysed using the Taft and Swain multiparametric equations. The rate constants correlate well with the Taft sigma* values; reaction constants being negative. A mechanism involving transfer of hydride ion has been suggested.