Structural analysis of a mesogenic 4-alkenyl bicyclohexylnitrile

The crystal and molecular structures of the mesomorphic compound having the molecular formula C5H9-C6H10-CN have been determined at 273 K. The compoun d crystallizes in a non-centrosymmetric orthorhombic system with the space group P2(1)2(1)2(1), and 4 molecules in the unit cell with cell dimensions a = 5.656 (1) Angstrom, b = 9.134 (2) Angstrom and c = 31.001 (6) Angstrom. Both cyclohexyl rings adopt chair conformations and are nearly coplanar. W ith regard to the crystal packing, contacts between the polar cyano groups cannot be observed and the molecules are stacked along the c-axis. Imbricat ed packing is a precursor to nematogenic behaviour. The molecular packing a nd phase sequences of this compound are compared with two other related com pounds. The effect of a double bond in specific terminal chain positions is discussed.