SELF-ASSOCIATION OF CHOLESTEROL IN BENZENE AND TOLUENE SOLUTIONS

The self-association of cholesterol in dilute benzene and toluene solu tions was investigated by conventional infrared spectroscopy. The samp le spectra, recorded in the fundamental OH stretching range, were reso lved into the bands of functionally different OH groups of associated cholesterol and its predominant species identified by analysis of thei r absorbances. The formation constants of oligomers were derived from monomer absorbances measured as a function of cholesterol concentratio n. In addition to the monomers A(1), open (A) over tilde(2) (Delta (H) over tilde(2) = -11 +/- 1 kJ mol(-1)) and cyclic dimers (A) over cap( 2) (Delta (H) over cap(2) = -24 +/- 2 kJ mol(-1)) in benzene and open dimers (A) over tilde(2) (Delta (H) over tilde(2) = -12 +/- 1 kJ mol(- 1)) and tetramers A(4) (Delta H-4 = -47 +/- 6 kJ mol(-1)) in toluene w ere established as the prevailing species. (C) 1998 Elsevier Science B .V. All rights reserved.