Hydrogen bonding abilities and self-association of some potentially bifunctional catalysts. Part 2. Mercaptoazole derivatives
Abstract
Hydrogen bonding abilities of 2-mercaptoazoles (1)–(3) towards dimethyl sulphoxide (KA) or 4-chlorophenol (KB) have been studied quantitatively in CCl4 by i.r. spectroscopy at 25 °C. The N–H proton of mercaptoazoles exhibits a high tendency to hydrogen bonding (40 < KA < 3 000 l mol–1) which is correlated with the basicity of the 2-alkylazole analogues. The CS sulphur atom shows good hydrogen bonding ability (20 < KB < 250 l mol–1) which roughly parallels its nucleophilic reactivity towards methyl iodide. Knowledge of the KA and KB constants allows a better understanding of the factors which affect the self-association constants of mercaptoazoles (100 < KD < 4 700 l mol–1).