Abstract
A new Schiff base ester, 3-hydroxy-4-{[(4-ethylphenyl)imino]methyl}phenyl octadecanoate, was synthesized and its IR, 1H NMR, 13C NMR and MS spectroscopic data are presented.
The mesomorphic behavior of an organic compound is basically dependent on its molecular architecture in which a slight change in the molecular geometry brings about considerable change in its mesomorphic properties. Many mesogenic homologous series contain two central linkages, both of which may either be ester [1] or Schiff base (CH=N) linking groups [2] or one of which may be an ester and the other one a Schiff base [3]. Schiff base esters possessing a long alkyl chain have received overwhelming attention due to their possibility to show liquid crystallinity properties such as smectic and nematic phases [4,5,6,7].
Synthesis
4-Formyl-3-hydroxyphenyl octadecanoate was previously prepared via Steglich esterification [8]. In a round-bottom flask, a mixture of the aldehyde (1.74 g, 5.0 mmol), 4-ethylaniline (0.61 g, 5.0 mmol) and absolute ethanol (40 mL) was refluxed for 3h with stirring. 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 (0.96 g, 39%).
Melting point: 86.2 oC
MS (EI): m/z = 507 (M+)
IR (KBr, cm-1): 3448 (O-H), 2955, 2917, 2848 (C-H aliphatic); 1758 (C=O ester); 1628 (C=N); 1607, 1472 (C=C aromatic).
1H NMR (400 MHz, CDCl3): δ/ppm 0.91 (t, 3H, J = 7.1 Hz, CH3), 1.27 (t, 3H, J = 7.3 Hz, Ar-CH2-CH3), 1.28-1.46 {m, 28H, CH3(CH2)14-}, 1.78 (quint, 2H, J = 7.5 Hz, -CH2CH2COO-), 2.58 (t, 2H, J = 7.4 Hz, -CH2COO-), 2.70 (q, 2H, J = 7.6 Hz, Ar-CH2CH3), 6.70 (dd, 1H, J = 2.2, 8.4 Hz, Ar-H), 6.77 (d, 1H, J = 2.2 Hz, Ar-H), 7.22-7.28 (m, 4H, Ar-H), 7.38 (d, 1H, J = 8.4 Hz, Ar-H), 8.63 (s, 1H, CH=N), 13.71 (s, 1H, OH).
13C NMR (100 MHz, CDCl3): δ/ppm 172.1 (COO), 161.2 (CH=N), 163.0, 154.8, 146.2, 143.8, 133.3, 129.2, 121.4, 117.6, 113.1, 110.8 (aromatic carbons), 34.9 (-CH2COO-), 25.3 (-CH2CH2COO-), 28.9 (Ar-CH2CH3), 32.3, 30.1, 30.0, 29.9, 29.8, 29.7, 29.6, 29.5, 23.1 (CH3(CH2)14-), 16.0 (Ar-CH2CH3), 14.5 (CH3(CH2)14).
Elemental analysis: Calculated for C33H49NO3 C, 78.06%, H, 9.73%, N, 2.76%; Found: C, 78.18%, H, 9.65%, N, 2.71%.
Supplementary materials
Supplementary File 1Supplementary File 2Supplementary File 3Acknowledgments
The author (S.T. Ha) would like to thank Universiti Tunku Abdul Rahman for the financial support and research facilities.
References and Notes
- Ha, S.T.; Yeap, G.Y.; Boey, P.L. Synthesis and smectogenic A and C* properties of (S)-(-)-2-methylbutyl 4’-(4”-n-alkanoyloxybenzoyloxy)biphenyl-4-carboxylates. Int. J. Phys. Sci. 2010, 5, 182–191. [Google Scholar]
- Kelker, H.; Scheurle, B. A liquid crystalline (nematic) phase with a particularly low solidification point. Angew. Chem. Int. Edn. 1969, 884–885. [Google Scholar] [CrossRef]
- Dave, J.S.; Kurian, G. Mesomorphic Behaviour of Schiff Base Esters-I: (a) p(p'-n-Alkoxybenzoyloxy)benzylidene-p”-anisidines (b)p(p'-n-Alkoxybenzoyloxy)benzylidene-p”-toluidines. Mol. Cryst. Liq. Cryst. 1977, 42, 175–183. [Google Scholar] [CrossRef]
- Yeap, G.Y.; Ha, S.T.; Lim, P.L.; Boey, P.L.; Ito, M.M.; Sanehisa, S.; Youhei, Y. Synthesis, physical and mesomorphic properties of Schiff’s base esters containing ortho-, meta- and para-substituents in benzylidene-4’-alkanoyloxyanilines. Liq. Cryst. 2006, 33, 205–211. [Google Scholar] [CrossRef]
- Ha, S.T.; Ong, L.K.; Wong, J.P.W.; Yeap, G.Y.; Lin, H.C.; Ong, S.T.; Koh, T.M. Mesogenic Schiff's base ether with dimethylamino end group. Phase Transit. 2009, 82, 387–397. [Google Scholar] [CrossRef]
- Ha, S.T.; Ong, L.K.; Ong, S.T.; Yeap, G.Y.; Wong, J.P.W.; Koh, T.M.; Lin, H.C. Synthesis and mesomorphic properties of new Schiff base esters with different alkyl chains. Chin. Chem. Lett. 2009, 20, 767–770. [Google Scholar] [CrossRef]
- Ha, S.T.; Ong, L.K.; Yasodha, S.; Yeap, G.Y.; Boey, P.L.; Lin, H.C. New mesogenic Schiff base esters with polar chloro substituent: synthesis, thermotropic properties and X-ray diffraction studies. Am. J. Appl. Sci. 2010, 7, 214–220. [Google Scholar] [CrossRef]
- Ha, S.T.; Ong, S.T.; Chong, Y.T.; Yeap, G.Y. Synthesis of 4-{[(3-chlorophenyl)imino]methyl}-3-hydroxyphenyl myristate. Molbank 2009, 2009, M629. [Google Scholar] [CrossRef]
© 2010 by the authors; licensee MDPI, Basel, Switzerland. This article is an open-access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/3.0/).