4-{[(4-Bromophenyl)imino]methyl}-3-hydroxyphenyl 4-(Hexadecanoyloxy)benzoate

Abstract

A new Schiff base ester, 4-{[(4-bromophenyl)imino]methyl}-3-hydroxyphenyl 4-(hexadecanoyloxy)benzoate was synthesized and its IR, ¹H NMR, ¹³C NMR and MS spectroscopic data are presented.

High demand for new liquid crystals (LCs) for applications has led to the preparation and study of numerous mesogens in particular, thermotropic liquid crystals [1,2]. Most thermotropic liquid crystals are calamitic molecules having a rigid core composed of two or more phenyl rings and one or more flexible terminal alkyl chains. Schiff base, also known as imine (CH=N), is one of the most well-known linking groups used in connecting the rigid core groups. Wide-ranging research on Schiff base core systems has been conducted since the discovery of MBBA which exhibited room temperature nematic phase [3]. Several studies have been conducted on ester-type Schiff bases owing to their interesting properties and substantial temperature range [4,5,6,7,8,9]. As a continuation of our previous work, we report here a new liquid crystal, 4-{[(4-bromophenyl)imino]methyl}-3-hydroxyphenyl 4-(hexa­decanoyl­oxy)benzoate.

Experimental

4-(4-n-Hexadecanoyloxybenzoyloxy)-2-hydroxybenzaldehye was prepared according to a method that we described in our previous work [10]. In a round-bottom flask, a mixture of the aldehyde (2.48 g, 5.0 mmol), 4-bromoaniline (0.86 g, 5.0 mmol) and absolute ethanol (40 mL) was refluxed with stirring for 3 h. The reaction mixture was filtered and the solvent was removed from the filtrate by evaporation. Recrystallization from absolute ethanol gave the title compound as a yellow solid (1.50 g, 46%).

Melting point: 222–224 °C

MS (EI): m/z (rel. int. %): 651 (M⁺, 1).

IR (KBr): ν_max/ cm⁻¹ 2950, 2916, 2848 (C-H aliphatic), 1754 (C=O of C₁₅H₃₁COO- fragment), 1743 (C=O of benzoate), 1623 (C=N), 1605 (C=C aromatic), 1282 (C-O).

¹H NMR (400 MHz, CDCl₃): δ/ppm 0.91 (t, 3H, J = 6.8 Hz, CH₃-), 1.24–1.45 (m, 24H, CH₃-(CH₂)₁₂-), 1.80 (quint, 2H, J = 7.4 Hz, -CH₂-CH₂COO-), 2.63 (t, 2H, J = 7.5 Hz, -CH₂-COO-), 6.87 (dd, 1H, J = 2.1, 8.4 Hz, Ar-H), 6.93 (d, 1H, J = 2.0 Hz, Ar-H), 7.20 (d, 2H, J = 8.6 Hz, Ar-H), 7.28 (d, 2H, J = 8.7 Hz, Ar-H), 7.47 (d, 1H, J = 8.5 Hz, Ar-H), 7.58 (d, 2H, J = 8.6 Hz, Ar-H), 8.26 (d, 2H, J = 8.7 Hz, Ar-H), 8.64 (s, 1H, CH=N), 13.20 (s, 1H, OH).

¹³C NMR (100 MHz, CDCl₃): δ/ppm 172.18 (C=O of C₁₅H₃₁COO-), 164.26 (C=O of benzoate), 162.56 (C=N), 162.96, 155.55, 155.17, 147.64, 133.83, 132.97, 132.31, 126.94, 123.26, 122.40, 120.94, 117.56, 113.58 and 111.08 for aromatic carbons, 34.83 (-CH₂COO-), 25.25 (-CH₂CH₂COO-), 32.36, 30.13, 30.11, 30.09, 30.08, 30.03, 29.88, 29.80, 29.68, 29.52, 29.43, 23.13 (CH₃(CH₂)₁₂), 14.58 (CH₃(CH₂)₁₂).

Elemental analysis: Calculated for C₃₆H₄₄NO₅Br, 66.46%, H, 6.82%, N, 2.15%; Found: C, 66.44%, H, 6.87%, N, 2.17%.