Hydrogen bonding in phenol + base complexes by n.m.r.

Abstract

The proton magnetic resonance spectra of solutions of phenol with various organic bases, employing carbon tetrachloride or dichloromethane as the solvent, were observed at 34.5 and –60°C respectively. The chemical shifts of the hydroxyl proton resonances of the 1 : 1 phenol + base hydrogen-bond complexes were measured. Corrections for the magnetic anisotropy of neighbouring groups, due to the donor base, were made to the chemical shift of the hydrogen-bonded phenolic proton. A linear correlation was shown to exist between the measured chemical shift and the dissociation constant of the organic base in aqueous solution. The correlation coefficients obtained as a result of the studies made at the two temperatures were increased by correcting for the anisotropy contribution to the chemical shift.