Thermodynamic Properties of Steroids: 5-cholesten-3β-ol, 5α-cholestan-3β-ol, and 5β-cholestan-3α-ol

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Thermodynamic properties such as melting point, enthalpy of fusion, and heat capacity for 5-cholesten-3β-ol (I), 5α-cholestan-3β-ol (II), and 5β-cholestan-3α-ol (III) were studied. The values of the melting point and the enthalpy of fusion for I were slightly larger than those for II, whereas the values for III were smaller than those for I and II. The heat capacity for I was to some extent larger than that for II or III in solid and even in liquid states. II is similar to I in the overall skeletal structure and in the direction of the OH moiety linking directly to the steroid ring. In addition, the X-ray powder diffraction pattern for II resembled that for I, whereas the pattern for III differed from that for I. The phase diagram for I/II mixture indicated that the I and II molecules are phase-separated in the solid state and give a eutectic mixture. The phase diagram results connecting with the data for the melting point, the enthalpy of fusion, and the heat capacity suggest that the cohesive force of I is stronger than that of II in spite of the similarity of I to II in the molecular and stacking structures. On the other hand, the phase diagrams of I/III and II/III mixtures indicated that I and III molecules and II and III molecules, whose OH moieties are in opposite directions to each other, made a strong 1 : 1 compound.
日本油化学会の論文
2001-09-01