Self-association of cholesterol in some chlorinated hydrocarbon solvents

Abstract

The self-association of cholesterol in dilute solutions in 1,2-dichloroethane, trichloromethane and tetrachlorormethane and over the temperature range 298–328 K was investigated using conventional infrared spectroscopy. The information on the size of the predominant cholesterol species was obtained by numerical processing of the solution spectra, recorded in the fundamental OH stretching range. Formation constants were derived from monomer absorbances measured as a function of cholesterol concentration. The following prevailing species and their enthalpies of formation were established: the monomer A 1 and monomer-solvent complex A 1* (Δ H 1*=−9±3 kJ mol −1) in 1,2-dichloroethane; the monomer and open dimer ( Ã 2) (Δ H̃ 2=−15.0±1.2 kJ mol −1) in trichloromethane; the monomer, open trimer ( Ã 3) (Δ H̃ 3=−31±3 kJ mol −1) and cyclic hexamer ( Â 6) (Δ Ĥ 6=−70±10 kJ mol −1) in tetrachloromethane.