Kinetic study of homogeneous acid-catalysed oxidation of certain amino-acids by potassium permanganate in moderately concentrated acidic media

Abstract

The rate of oxidation of glycine, DL-alanine, DL-valine, and DL-leucine by potassium permanganate in aqueous sulphuric and perchloric acid solution is proportional to the concentration of the amino-acid. For each amino-acid, the total order of the reaction is two at a given concentration of sulphuric and perchloric acid. The rate of oxidation of the amino-acids is greater in sulphuric than in perchloric acid for the same concentration. Various hypotheses for the mechanism of acid catalysis have been tested and it has been found that the rate is related to the activity of water in accord with Bunnett's hypothesis. There is no primary salt effect, but at higher concentrations of added neutral salts, the logarithm of the rate constant is linearly related to ionic strength. Specific ionic effects have also been found. The energy and entropy of activation and frequency factor have been calculated and a mechanism in agreement with the observations is suggested.