Synthesis and Mesomorphic Properties of 3,5-bis-(p-n-Alkoxyphenyl)lsoxazole and 3,5-bis-(p-n-Alkoxyphenyl)Pyrazole

The synthesis and mesomorphic behavior of 3,5-bis-(p-n-alkoxyphenyl)isoxazole (series I) and 3,5-bis-(p-n-alkoxyphenyl)pyrazole (series II) are reported for the number of carbon atoms (n) in the alkoxy chains varying from three to eight. Series I shows an enantiotropic nematic phase for all n and an enantiotropic smectic phase for n ⩾ 6. Series II shows one smectic phase SI for all n and an additional smectic phase SII for n ⩾ 6. From optical and X-ray data, the smectic phase of series I is identified as smectic C and in series II the SI phase is classified as smectic A and SII as a smectic C with a temperature dependent tilt angle. The 1-methyl substituted pyrazole was prepared and did not show mesophases.