Kinetics and mechanism of oxidation of aliphatic aldehydes by pyridinium chlorochromate

583-587Oxidation of six aliphatic aldehydes by pyridinium chlorochromate (PCC), in dimethyl sulphoxide (DMSO), to the corresponding carboxylic acids, is first order each in PCC, the aldehyde and hydrogen ion. The oxidation of deuteriated acetaldehyde, MeCDO, exhibits a substantial primary kinetic isotope effect (kH/kD = 6.12 at 288 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 σ* values; reaction constants being negative. A mechanism involving transfer of hydride ion has been suggested