Reactivity of the halogenothiazoles toward nucleophiles. Part III. Kinetics and mechanisms of the reaction between 4(5)-X-2-halogenothiazoles and substituted thiophenols

Abstract

4(5)-X-2-Halogenothiazoles react with un-ionised thiophenol to give the normal substitution products [4(5)-X-2-phenylthiothiazoles]. The effects of structural changes in the thiazole and in the thiophenol operate in the sense opposite to that observed in normal nucleophilic substitutions and emphasise the existence and importance of a pre-equilibrium (of the acid–base type) between the thiazole and the thiophenol which precedes the substitution step. The effect of added acid is also considered.