Effects of Lateral Substituents on Mesomorphic Behavior. III. N-4-(4-Alkoxybenzoyloxy)benzylidene]-anilines

The mesomorphic properties of N-4-(4-alkoxybenzoyloxy)benzylidene]-2- and -3-X-anilines, where X = Me, F, Cl, Br or I, were examined. The 2-Me derivatives give higher nematic-isotropic transition temperatures than the 3-Me derivatives, whereas the reverse is true for the F compounds. The intersection between the plots of the transition temperatures of the 2-X and 3-X derivatives against the alky chain length is found for the CL, Br, and I compounds, respectively. The smectic A-nematic transition temperature recorded for the heptyloxy member is promoted by the 3-X substitution as much as 32°C (X = F) and 16° (X = Cl).