Kinetics and mechanism of the transalkylation between some alkyl heterocyclic ethers and thiophenol

Abstract

The transalkylation between some ring-nitrogen activated alkyl heterocyclic ethers and thiophenol has been studied quantitatively for alkoxy-1-methylbenzimidazoles. The influence of structural changes of the alkoxy-moiety and of the benzene nucleus on the basicity and reactivity of the system has been investigated. The results are consistent with a reaction mechanism where a rapid acid–base equilibrium between thiol and ether was established, followed by an S_N2 attack by ArS^– at the ether saturated carbon atom. 1-Methyl-2-methylthiobenzimidazole did not react with thiophenol: this fact was interpreted in terms of the low electron-donating ability of the sulphur atom of the sulphide.