Proton magnetic resonance spectra and the intramolecular hydrogen bonding of o-alkoxy- phenols and -benzenethiols

The PMR spectra of several methoxy substituted benzenethiols and related phenols have been examined in various solvents over a wide range of concentrations. The positions of the sulfhydryl proton resonance signals (δ_SH) of o-methoxybenzenethiol and 2,6-dimethoxybenzenethiol in inert solvents, and the δ_SH values of the thiols carrying o-OMe groups are less affected by the interaction with the solvents than those without o-OMe groups. The significant differences in the behaviour of chemical shifts of these compounds have been best interpreted by the intramolecular S---HO H-bonding. Additional evidence for the intramolecular H-bonding in o-OMe substituted benzenethiols have been obtained from the IR spectroscopic data.