Hydrogen bonds between cholesterol and oxygen bases: a thermodynamic study

Using calorimetric and IR spectroscopic methods, the values of thermodynamic functions of (1 : 1) hydrogen-bond complex formation between cholesterol and some proton acceptors in CCl4 have been determined. The self-association of cholesterol in the solvent used was taken into account in calculations. The proton acceptors used are oxygen bases containing CO, —O—, PO and SO groups. The values of ΔfH were compared with those previously obtained for the pure bases. The enthalpy of hydrogen-bond complex formation of cholesterol is a linear function of Gutmann's donor number for all the proton acceptor compounds examined. Badger–Bauer's relation {ΔfH=f[Δv(OH)]} is not satisfied as well as ΔfH=f(DN) but it allows the prediction of values of enthalpy of complex formation between cholesterol and proton acceptors within ± 1.5 kJ mol–1 limits.