Anion–molecule complexes in solution. III. Nuclear magnetic resonance studies of halide ion–alcohol association

Abstract

Certain alkyl-, aryl-, and arene-substituted alcohols form linear, hydrogen bonded complexes with bromide and other halide ions in tetrachloromethane. The hydroxyl proton shifts ca. 4 p.p.m. downfield in the complex, regardless of the degree or type of substitution. The interaction is enhanced by inductive electron withdrawal by substituents on the C—O—H moiety. A comparison of the present results with infrared spectroscopy shows that the absorption at ca. 3300 cm⁻¹ is entirely due to 1:1 alcohol–anion complexes. The a coefficient in Buckingham's equation for electrostatic interaction of a molecule with an ion, δσ_E = aE_z−bE², is found to be 5.5 for alcohol O—H bonds.