Kinetics and mechanism of oxidation of aliphatic aldehydes by 2, 2' –bipyridinium chlorochromate

1169-1173Oxidation of six aliphatic aldehydes by 2, 2'-bipyridinium chlorochromate (BPCC) in dimethyl sulphoxide (DMSO) leads to the formation of corresponding carboxylic acids. The reaction is first order each in BPCC and the aldehyde. The reaction is catalysed by hydrogen ions. The hydrogen-ion dependence has the form: kobs = a + b[H+].The oxidation of deuteriated acetaldehyde, MeCDO, exhibits a substantial primary kinetic isotope effect (kH/kD = 5.90 at 298K). 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 σ* values; reaction constants being negative. A mechanism involving transfer of hydride ion has been suggested