Intramolecular hydrogen bonds in aromatic sulphoxides: 1H nuclear magnetic resonance and acidity constant measurements

Abstract

Comparative examination of the ¹H n.m.r. chemical shifts and acidity constants of o-methylsulphinylphenol and o-hydroxyacetophenone shows that intramolecular hydrogen bonding is stronger for the carbonyl compound. The effect of bulky groups ortho to the SOCH₃ and COCH₃ groups indicates that these have different intramolecular hydrogen bonding patterns and different stereochemical requirements for molecular stabilization, when attached to an unsaturated system. Parallel behaviour is also found for the corresponding amino-derivatives. Possible electronic interactions between the sulphinyl group and the unsaturated ring in aromatic sulphoxides are discussed.