The Mesomorphic Behavior of Stigmasteryl Carbonates

Abstract

Starting from stigmasterol, phosgene and normal alcohols or alkandiols, two homologous series of stigmasteryl derivatives were synthesized, namely, the n-alkyl stigmasteryl carbonates and the α,λ-polymethylen bis(stigmastery1) carbonates. Some of the chloroformates required as intermediates were prepared and isolated. Purification of all stigmasteryl carbonates was achieved by column chromatography using silica gel as adsorbent and benzene ligroine mixtures as the developing solvent system. The same combination was employed in thin layer chromatography to monitor the purity of reaction products and to identify side products. Physical and analytical data are compiled in two tables. Physical investigations revealed that none of the compounds showed a cholesteric phase, but some of them displayed smectic phases on cooling of their isotropic liquids. A heavily contaminated sample, however, showed iridescent colors, which subsequently could be obtained from pure stigmasteryl carbonates by the addition of stigmasteryl derivatives which by themselves do not show mesophases.