MOLECULAR-STRUCTURE AND CONFORMATIONAL-ANALYSIS OF CHIRAL YLIDENE)-1-ISOPROPYL-2-METBOXY-4-METHYLCYCLOHEXEDE

lidene)-1-isopropyl-2-methoxy-4-methylcyclohexene, capable of inducing spiral supramolecular ordering when introduced to nematic and some sm ectic mesophases, has been studied by an X-ray structural analysis. Th e crystals are orthorhombic; at 20 degrees C a = 6.055(1), b = 13.282( 3), c = 20.734(4) Angstrom, V = 1668(1) Angstrom(3), d(calc) = 1.380 g cm(-3), space group P2(1)2(1)2(1), Z = 4 The cyclohexene ring has a c onformation intermediate between a sofa and a half-chair. The methyl a nd methoxyl groups are in a syn orientation with respect to the mean p lane of the cycle. The angle between the plane of the aryl substituent and the exocyclic double bond is 33 degrees. The observed distortions of bond angles at unsaturated carbon atoms are typical of derivatives of benzylidenecyclohexene. Molecular mechanics calculations demonstra ted that the conformation observed in the crystalline state is not the most favorable, and this conformation is stabilized through intermole cular interactions upon stacking in crystals. It was shown that the re lative orientation of the methyl and methoxyl groups as well as the or ientation of the aryl substituent substantially affect the conformatio n of the cyclohexene ring.