Síntese de cristais líquidos derivados dos heterociclos oxazol e tetrazol

by dos Santos, Daniela Rubia

This work describes the synthesis, the characterization and the study of the mesomorphic properties of two new homologous series of derived compounds of 4-[5-(2-n-alkyltetrazolyl)]-phenyl-3-carboxy-5´-(4?-octylphenyl)-isoxazole ( Series I ) and 4-[5-(2-n-alkylltetrazolyl)]-phenyl-5-benzoyloxy-3-(4-octyloxyphenyl)-1,2,4-oxadiazole (Series II). The synthetic methodology used was efficient, where 4- cyanophenol was used as starting material for thepreparation of the tetrazoles and 1,2,4-oxadiazoles precursors. The isoxazoles intermediates were synthesized departing from the 4-hydroxyacetophenone, through Williamson´s etherification, condensation,cyclization and hydrolysis reactions, obtaining the isoxazole acid. In order to obtain liquid crystals an esterification between the tetrazoles and isoxazoles precursors ( series I) and the 1,2,4-oxadiazoles and tetrazoles precursors ( series II ) wascarried out. All the synthesized compounds have shown mesomorphic properties of enantiotropic smectic C and nematic types for composites of series I, and enantiotropicsmectic C, smectic A and nematic for the series II. In order to characterize the obtained compounds the following techniques were used: IR spectroscopy, 1H NMR, 13C NMR,elemental analysis and optical microscopy of polarized light