Preparation of chloro-substituted liquid crystals containing azobenzene moieties

Hui, Kok Keng (2007) Preparation of chloro-substituted liquid crystals containing azobenzene moieties. Universiti Malaysia Sabah. (Unpublished)

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Abstract

Ethyl-4-aminobenzoate was used as the starting material, and undergone diazo coupling reaction with phenol to produced 4-(4-hydroxyphenylazo)-ethyl benzoate. Then, the product formed was reacted with bromohexane via Williamson ether synthesis to yield 4-( 4-hexyloxyphenylazo)-ethyl benzoate. After that, the ester compound was proceeded to base-catalysed hydrolysis using potassium hydroxide to yield 4-( 4-hexyloxyphenylazo )-benzoic acid. Finally, the benzoic acid was reacted with 4-chlororesorcinol, to this catalytic amount of 4-dimethylaminopyridine (DMAP) was added as catalyst and 1,3-dicyc1ohexylcarbodiimide (DCC) as a dehydrating agent. The expected final compound was l-chloro-2,4-phenylene-bis-[ 4-( 4- hexyloxyphenylazo)-benzoate], with the total yield of 0.227g (68.29% of percentage yield) and melting point at the range of 195 to 199°C. However FT-IR spectrum of the final compound showed that it was lacked of carbonyl group (C=O) of ester and complete assignment of the 1H-NMR also could not be made due to the present of impurities. Therefore, the preparation of chloro-substituted liquid crystals containing azobenzene moieties was not successful, this might be due to the operative errors such as personal errors that occurred during the synthesis steps. The final compound possibly a mixture of benzoic acid and 4-chlororesorcinol. The thermal behaviour of the fmal compound was investigated using differential scanning calorimeter (DSC) and the DSC thermogram which showed that there was no existence of mesophase for the final compound.

Item Type: Academic Exercise
Uncontrolled Keywords: ethyl-4-aminobenzoate, bromohexane, potassium hydroxide, base-catalysed hydrolysis, chloro-substituted liquid crystal
Subjects: Q Science > QD Chemistry
Divisions: SCHOOL > School of Science and Technology
Depositing User: MDM SITI AZIZAH IDRIS
Date Deposited: 21 Jun 2013 03:49
Last Modified: 23 Oct 2017 04:49
URI: http://eprints.ums.edu.my/id/eprint/6366

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