A novel reaction of some enolisable ketones not involving the rate-determining enolisation step. Kinetics of the reaction of ketones with trichloroisocyanuric acid in the presence of added chloride ion in acid medium

Abstract

Kinetics of the reaction between some enolisable ketones (S) and trichloroisocyanuric acid (TClCA) in aqueous acid–acetic acid medium at 35 °C follow pseudo-zero-order and pseudo-first-order disappearance of [TClCA]₀ in the absence and the presence of added Cl^–, respectively. The rate constants for the latter system exhibit a linear dependence each on [S]₀ and [H⁺], and an increasing and limiting dependence on added [Cl^–]. The results are 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 Cl^– and (ii) rate-determining interaction of SH⁺ with the most effective molecular chlorine species produced by the hydrolysis of TClCA (rather than a rate-determining interaction of enol with Cl₂) in the presence of added Cl^–, prior to the rapid steps of product formation.