The kinetics of the oxidation of aliphatic aldehydes, formaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, and trichloroacetaldehyde by Peroxomonosulphate (PMS) was carried out in aqueous perchloric acid medium (0.1-1 M H+) a t constant ionic strength of 1.2 M in the temperature range 1O"-6O0C. The reactions of all the aldehydes were found to obey a total second-order kinetics, first order each with respect to [Peroxomonosulphatel and [aldehyde]. Acetaldehyde, propionaldehyde, and n-butyraldehyde exhibited acid catalysis with the concurrent occurrence of acid-independent reaction path conforming to the rate law
dt Formaldehyde was found to undergo oxidation only by acid-dependent path (kb = 0) and trichloroacetaldehyde exhibited only the acid-independent reaction path ( k , = 0). The products of oxidation were found to be the respective carboxylic acids in each case. The stoichiometry of the reaction, [Peroxomonosulphatel :[Aldehyde] = 1 : 1, indicated the absence of carbonyl-assisted decomposition and self-decomposition of peroxomonosulphate. The kinetic and thermodynamic parameters evaluated pointed to the mechanism of a fast nucleophilic attack of the oxidant on the aldehyde followed by slow acid catalyzed and/or uncatalyzed decomposition of the intermediate to product. A sharp comparison is made with the corresponding reactions of the similar peroxides, S,Og- and H,PO;.