NOVEL MESOGENIC BENZOIC-ACIDS WITH LARGE BRANCHES .1. SYNTHESIS, LIQUID-CRYSTALLINE PROPERTIES AND CRYSTAL-STRUCTURE ANALYSES OF NZYLOXYCARBONYL)-4-(4-N-OCTYLOXYBENZOYLOXY)BENZOIC ACIDS

New benzoyloxybenzoic acids bearing both terminal and lateral groups h ave been synthesized. Substituted aryl rings are laterally attached to the basic mesogens by means of an odd-numbered spacer. Therefore, liq uid crystalline behaviour can be observed at high temperatures. The cr ystal and molecular structure of enzyloxycarbonyl)-4-(4-n-octyloxybenz oloxy)benzoic acid 3b has been determined by X-ray analysis. 3b crysta llizes in space group P2(1)/n with four molecules in a unit cell of th e following dimensions: a = 15.682(2), b = 7.701(1), c = 23.107(3) Ang strom, beta = 97.69(1)degrees. The structure was solved by direct meth ods and refined to an R value of 0.057 for 3684 observed reflections. The molecules of 3b are associated to dimers with a shape unusual for mesogens exhibiting nematic and smectic phases. In the crystal the dim ers are closely packed to ribbons which on their part are connected to lamellar sheets. The nitro-substituted homologue 3c was proved to be isostructural with 3b.