The proton magnetic resonance spectra of phenol in the absence of intermolecular proton exchange

Abstract

The proton magnetic resonance spectra in the absence of intermolecular proton exchange for 0.27, 0.59, and 0.79 M solutions of phenol in CCl4 are analyzed. The long-range coupling over five bonds between the hydroxyl and ring protons is estimated as 0.33 Hz in the monomer and as 0.20 Hz in the trimer of a monomer–trimer model. Support for the decrease in the coupling on trimerization is found in CNDO/2 and INDO MO FPT calculations. The long-range coupling over six bonds is unobservable, consistent with conformations of the trimer in which the phenol molecules remain planar. Water catalyzes the intermolecular proton exchange and, in its absence, the transfer of hydroxyl protons from molecule to molecule within the associated species is inefficient.