Liquid Crystalline Pyridine Containing 1,2,4-Oxadiazoles

New mesomorphic 1,2,4-oxadiazoles containing as an electron-acceptor substituent the pyridine cycle with different position of the nitrogen atom with respect to the oxadiazole cycle have been synthesized. The reaction of the isonicotinic and nicotinic amidoximes with various acid chlorides smoothly provided the corresponding mesogenic 3-(4-pyridinyl)- and 3-(3-pyridinyl)-1,2,4-oxadiazoles. On the contrary with picolinic amidoxime as a starting material mainly the uncyclizated nonmesomorphic products were obtained. Temperature and dielectric characteristics of new pyridinic liquid crystals were measured and compared with analogous parameters of corresponding phenyl (cyclohexyl) substituted oxadiazoles.