Mixed association of cholesterol with methyl cholate and methyl lithocholate in chloroform solutions

The concentration-dependent mixed association behavior of cholesterol with methyl cholate (MeC) and methyl lithocholate (MeLC) in chloroform at 37 degrees C has been studied by vapor pressure osmometry (VPO). This study is part of a larger project to investigate the effect of number and position of hydroxyl-bearing steroids. Using theories developed by Adams and by Steiner, the model and appropriate parameters for the nonideal mixed associations were elucidated. For the MeLC/cholesterol system, no mixed association was observed. For the MeC/cholesterol system, both methods of analysis indicate that a nonideal AB complex formation occurs. The best parameters to explain the experimental data are kAB = 0.04 1/g; BAB (the nonideal term) = 1.5 X 10(-5) 1 mol g-2.