Self-association of cholesterol in benzene and toluene solutions

Abstract

The self-association of cholesterol in dilute benzene and toluene solutions was investigated by conventional infrared spectroscopy. The sample spectra, recorded in the fundamental OH stretching range, were resolved into the bands of functionally different OH groups of associated cholesterol and its predominant species identified by analysis of their absorbances. The formation constants of oligomers were derived from monomer absorbances measured as a function of cholesterol concentration. In addition to the monomers A 1, open à 2 (Δ H̃ 2=−11±1 kJ mol −1) and cyclic dimers  2 (Δ Ĥ 2=−24±2 kJ mol −1) in benzene and open dimers à 2 (Δ H̃ 2=−12±1 kJ mol −1) and tetramers A 4 (Δ H 4=−47±6 kJ mol −1) in toluene were established as the prevailing species.