2002 Volume 51 Issue 1 Pages 11-17
Phase diagrams for binary mixtures of sterols such as 5-cholesten-3β-ol (I), 5α-cholestan-3β-ol (II), 5β-cholestan-3α-ol (III) and 5β-cholestan-3β-ol (IV) were studied. II is similar to I in its straight, plank-like skeletal structure and in the direction of OH moiety linking directly to the steroid ring. III is similar to IV in its bending skeletal structure and differs in the direction of OH moiety from I, II and IV. From phase diagrams for all of their binary mixtures, it became clear that in I/II and also in II/IV systems the molecules of each component are phase-separated from each other in the solid state and provide a eutectic mixture. In I/III, II/III and III/IV systems, two kinds of molecules whose OH moieties are in opposite directions to each other made a 1:1 compound. On the other hand, in I/IV system I and IV molecules made an incongruent melting (peritectic) compound, which was less stable and, before its melting, decomposed into solid I and a 1:1-molar-ratio solution of I and IV at 373 K.
