Liquid-Crystalline Solvents as Mechanistic Probes. 18. The Micromorphology of Crystalline and Liquid-Crystalline Phases of 5α-Cholestan-3β-yltrans-Cinnamate as Discerned from Photochemical Studies1

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Abstract
The photoreactions of 5α-cholestan-3β-yl trans-cinnamate in its crystalline and liquidcrystalline phases and in isotropic solutions (n-hexane and n-hexadecane) have been investigated. In hydrocarbon solutions, geometric isomerization of the ester and its cleavage to cholestene and cinnamic acid are the dominant processes; in the crystalline and liquid-crystalline phases, dirnerization is the principal reaction mode. Only one photodimer, bis(5α-cholestan-3β-yl) α-truxillate (head-to-tail), could be detected from the crystalline and liquid-crystalline phase experiments. The photochemistry of the liquid-crystalline phase of cholesteryl trans-cinnamate was reexamined and shown to proceed quite differently from that of the cholestanyl ester.