CRYSTAL-STRUCTURES OF 2 MESOGENIC, LATERALLY SUBSTITUTED DICYCLOHEXYLETHANE DERIVATIVES

The structures of the solid-crystalline smectic-B precursor phases of 1,2-bis(4-pentylcyclohexyl)ethan-1-ol (1) and 1,2-bis(4-pentylcyclohex yl)ethan-1-one (2) have been investigated by X-ray analysis. Both comp ounds crystallize in the same space group P (1) over bar with Z = 1 an d the following lattice parameters: a = 10.945(3), b = 10.238(3), c = 5.404(2) Angstrom, alpha= 75.08(2), beta = 86.94(2), gamma = 78.80(2)d egrees, V = 574.0(3) Angstrom(3) for 1 and a = 10.814(2), b = 10.097(2 ), c = 5.438(1) Angstrom, alpha = 76.68(2), beta = 90.12(1), gamma = 8 0.83(2)degrees, V = 569.9(2) Angstrom(3) for 2. The unit-cell content of one molecule requires a molecular structure which is realized by a special kind of disorder of the perfectly parallel-aligned molecules w ithin the crystal packing. For 1, weak O-H ... O hydrogen bonds have b een observed. The results are compared with those for the laterally un substituted 1,2-bis(4-pentylcyclohexyl)ethane (3). All three are isost ructural.