Reactions of enolisable ketones with dichloroisocyanuric acid in absence and presence of added chloride ions – a kinetic study

Abstract

Kinetics of reactions of enolisable ketones (S = acetone/2-butanone) with dichloroisocyanuric acid (DCICA) were studied in aqueous acetic acid and perchloric acid media in absence and presence of added chloride ions. The reactions were found to be pseudo zero order and pseudo first order on [DCICA] in absence and presence of chloride ions respectively. Both in presence and absence of chloride ions, first order and fractional order in substrate and perchloric acid were observed respectively. An increase in the rate of reaction was observed with an increase in chloride ion concentration as well as acetic acid composition. The results were interpreted in terms of probable mechanisms involving (i) rate-determining enol formation from the conjugate acid of the ketone (SH⁺) in the absence of added chloride ions and (ii) rate-determining interaction of SH⁺ with the most effective molecular chlorine species produced by the hydrolysis of DCICA (rather than a rate-determining interaction of enol with chlorine) in the presence of added chloride ions, prior to the rapid steps of product formation.

KEY WORDS: Dichloroisocyanuric acid, Acetone, 2-Butanone, Kinetics, Chloride ion, Enolisation

Bull. Chem. Soc. Ethiop. 2015, 29(1), 129-136

DOI: http://dx.doi.org/10.4314/bcse.v29i1.12