Author name:
زينب حسن فليح
Supervisor name:
نسرين رحيم جبر
Abstract:
This study is concerned with the synthesis and characterization of two new series 3 - (4 - pentoxyphenyl) - 5 - (4΄ - substituted phenyl) - 1,2,4 - oxadiazole and 3 - (4 - pentoxy benzoyloxyphenyl) - 5 - (4΄ - alkoxy benzoyloxy phenyl) - 1,2,4 - oxadiazole of fifteen new compounds.The first series 3 - (4 - pentoxyphenyl) - 5 - (4΄ - substituted phenyl) - 1,2,4 - oxadiazole of ten compounds with the structural formula(6)a - jThis was prepared as following : at first by reaction of p - hydroxy benzaldehyde (1) with hydroxyl amine hydrochloride to give p - hydroxy benzaldoxime (2) which then dehydrated by acetic anhydride to give p - hydroxy benzonitrile (3). Alkylation of compound (3) give p - pentoxy benzonitrile (4) and this compound react with hydroxyl amine hydrochloride to give 4 - petoxy benzamidoxime (5) which finally react with p - substituted benzoyl chloride to give 3 - (4 - pentoxyphenyl) - 5 - (4΄ - substituted phenyl) - 1,2,4 - oxadiazole (6)a - j.VINNOC5H11OXX= CnH2n+1 (n=1 - 5) ,F,Cl , Br,I and NO2The second series 3 - (4 - pentoxy benzoyloxyphenyl) - 5 - (4΄ - alkoxy benzoyloxyphenyl) - 1,2,4 - oxadiazole includes five compounds, , with the structural formula ONNOOCOC5H11OCOOCnH2n+1(11)a - en = 1 - 5This was prepared as following : p - hydroxy benzonitrile (3) react with p - pentoxy benzoyl chloride to give of p - pentoxy benzoyloxy benzonitrile (7) this compound reacted with hydroxylamine hydrochloride to give p - pentoxy benzoyloxy benzamidoxime (8) than finally reacted with p - alkoxy benzoyloxy benzoyl chloride to give 3 - (4 - pentoxy benzoyloxyphenyl) - 5 - (4΄ - alkoxy benzoyloxyphenyl) - 1,2,4 - oxadiazole (11)a - e.All the synthesized compounds were characterized by FTIR spectroscopy.The compounds 3 - (4 - pentoxy phenyl) - 5 - (4΄ - butoxy phenyl) - 1,2,4 - oxadiazole,3 - (4 - pentoxy phenyl) - 5 - (4΄ - chlorophenyl) - 1,2,4 - oxadiazole , 3 - (4 - pentoxy benzoyloxy phenyl) - 5 - (4΄butoxy benzoyloxy phenyl) - 1,2,4 - oxadiazole and 3,5 - (4,4 - pentoxy benzoyloxy phenyl) - 1,2,4 - oxadiazole were also characterized by 1HNMR.The liquid crystalline behaviors of the two series have been examined by means of hot - stage polarizing microscopy for the determination of phase transition temperatures and the type of mesophases. Microscopic observations of first series compounds at liquid crystalline transition temperature displayed a nematic mesophase of typical nematic droplets are observed on cooling from the isotropic liquid for compounds 3 - (4 - pentoxy phenyl) - 5 - (4΄ - propoxy phenyl) - 1,2,4 - oxadiazole (6)c, 3 - (4 - pentoxy phenyl) - 5 - (4΄ - butoxy phenyl) - 1,2,4 - oxadiazole (6)d and 3 - (4 - pentoxy phenyl) - 5 - (4΄ - pentoxy phenyl) - 1,2,4 - oxadiazole(6)e , while compounds 3 - (4 - pentoxy phenyl) - 5 - (4΄ - methoxy phenyl) - 1,2,4 - oxadiazole (6)a and 3 - (4 - pentoxy phenyl) - 5 - (4΄ - ethoxy phenyl) - 1,2,4 - oxadiazole (6)b did not show any liquid crystalline properties. Compounds 3 - (4 - pentoxy phenyl) - 5 - (4΄ - floro phenyl) - 1,2,4 - oxadiazole (6)f and 3 - (4 - pentoxy phenyl) - 5 - (4΄ - iodo phenyl) - 1,2,4 - oxadiazole (6)i also did not show any mesomorphic properties, while compounds 3 - (4 - pentoxy phenyl) - 5 - (4΄ - chloro phenyl) - 1,2,4 - oxadiazole (6)g and 3 - (4 - pentoxy phenyl) - 5 - (4΄ - bromo phenyl) - 1,2,4 - oxadiazole (6)h show a nematic droplets mesophase. Compound 3 - (4 - pentoxy phenyl) - 5 - (4΄ - nitro phenyl) - 1,2,4 - oxadiazole (6)j shows monotropic smectic A and nematic phases.Liquid crystalline properties of compounds 3 - (4 - pentoxy benzoyloxy phenyl) - 5 - (4΄ - alkoxy benzoyloxyphenyl) - 1,2,
