Dielectric studies. Part 8.—Hydroxyl re-orientation in intramolecularly hydrogen-bonded phenols

Abstract

The dielectric absorption of some intramolecularly hydrogen-bonded phenols in dilute p-xylene solution has been determined at four or five microwave frequencies and the static dielectric constant at 1 Mc/sec. The dielectric data have been analyzed to yield relaxation times and dipole moments. Strongly intramolecularly hydrogen-bonded phenols such as salicylaldehyde are characterized by one relaxation time whereas weakly intramolecularly hydrogen bonded compounds such as o-chloro-phenol yield a molecular relaxation time and one for hydroxyl re-orientation.

Although the cis and trans forms of the o-substituted phenols have different energies of activation for hydroxyl re-orientation, the data have been interpreted in terms of one hydroxyl relaxation time. Theories by Garton and by Hoffman and Pfeiffer appear to offer a satisfactory explanation for only one intramolecular relaxation time.