Self-Association of Phenol in Nonpolar Solvents

Abstract

The self-association of phenol in carbon tetrachloride solution has been studied extensively by a variety of techniques, but our understanding of the process is still incomplete. Using data obtained on the second overtone O—H stretching bands of phenol, Kempter and Mecke⁽¹⁾ concluded in 1940 that a series of multimers is formed and that a single constant is sufficient to describe the entire process. In 1951, Coggeshall and Saier⁽²⁾ carried out a similar study in the fundamental O—H stretching region and obtained better agreement between theory and experiment by using two equilibrium constants, one for the formation of dimer and one for the successive addition of monomeric units to form higher polymers. In 1958, Saunders and Hyne⁽³⁾ studied the self-association process by nuclear magnetic resonance and concluded that a model based upon a monomer-trimer equilibrium provided the best fit for the experimental data. Delvalle,⁽⁴⁾ in 1961, reported vapor-pressure data which supported the single-equilibrium-constant model of Kempter and Mecke. About the same time, Badger and Greenough⁽⁵⁾ concluded, from partition and spectroscopic experiments, that the association of phenol in carbon tetrachloride solution is greatly promoted by the presence of water and that the predominant polymer species is a hemihydrate dimer. More recently, however, Johnson et al. ⁽⁶⁾ have interpreted the results of partition experiments in terms of a monomer-trimer-hexamer model involving both anhydrous and hydrated species.

The authors gratefully acknowledge the contributions of Mr. T. A. Odom, Jr., who wrote the computer programs and offered much valuable advice concerning the computational aspects of this problem. The assistance of Mrs. Juanita Collins in all phases of the experimental work and in coding the data for computer treatment is appreciated.