Synthesis, characterisation and mesomorphic behaviours of non-symmetrically substituted 1,2,4- and 1,3,4-oxadiazole derivatives

Abstract

All the starting materials required for the synthesis were produced from sigma-Aldrich Company and used as received without further purification. Most the intermediate compounds in this study were prepared according to the procedures in our references [20] and [21] with a few simple modifications. The structures of all intermediates and more of final products were characterized by spectroscopic methods. FT-IR spectra of solid sample in ATR technique were recorded on Shimadzu 8400S, 1 H NMR spectra were obtained with Bruker spectrophotometer model ultrashield at 300 MHz using tetramethylsilane (TMS) as interval standard and CDCl3, DMSO-d6 as solvents. Elemental analysis for carbon, hydrogen and nitrogen were conducted using a Perkin-Elmer model 2400 instrument. Mass spectra of some compounds were recorded on Shimadzu QP1000EX using (SCI) mode. Investigation the liquid crystals properties of the final compounds were carried out by polarized optical microscopy (POM) model PW-BK 5000 PR equipped with a hot-stage system of HS-400 (KER 3100-08S). Phase transition temperatures were recorded by differential scanning calorimetry (DSC) model Linseis instrument STA PT-1000, Ramp rate: 5 °C/ min. on heating and cooling, temperature and heat flow calibrated with standard indium with heating and cooling rates of 5 °C/min -1 . Synthesis Methyl p-toluate [A]This compound was prepared by classical esterification method described by Chiang et al. [22].