Infrared study of the adsorption of phenols on silica immersed in heptane

Abstract

Infrared spectra of silica immersed in heptane solutions of eleven phenols have been recorded as a function of adsorbate concentration. Two main types of surface-adsorbate interaction have been characterized, one involving the formation of hydrogen bonds between surface silanol groups and the aromatic π-electron systems of adsorbed molecules, and the other involving hydrogen bonds between silanol groups and the phenolic hydroxy groups of adsorbed species. The spectroscopic results are discussed in terms of the electronic and steric effects of ring-substituents on the two types of adsorptive interaction. Infrared spectroscopy provides a powerful technique for the study of surface species in situ at the oxide/hydrocarbon interface.