Steric and electronic effects on self-association of potentially bifunctional catalysts: Δ4-thiazoline-2-thiones

Abstract

The self-association in CCl₄ of some 4,5-dialkyl-Δ⁴-thiazoline-2-thiones (1) has been studied by i.r. spectroscopy. The experimental data can be explained in terms of an equilibrium between monomer and cyclic dimer. Both steric and electronic effects affect the self-association constant K. The increase in K parallels the increase in nucleophilicity of the sulphur atom. The steric effect of substituents ortho to the N–H bond decreases the self-association constant. These two factors which specifically affect the nucleophilic or the electrophilic centre are useful in the design of bifunctional catalysts.