4-(4-Propoxybenzo­yloxy)benzoic acid

Khushi Muhammad; M Khawar Rauf; Masahiro Ebihara; Shahid Hameed

doi:10.1107/S1600536808016942

. 2008 Jun 13;64(Pt 7):o1251. doi: 10.1107/S1600536808016942

4-(4-Propoxybenzoyloxy)benzoic acid

Khushi Muhammad ^a, M Khawar Rauf ^a, Masahiro Ebihara ^b, Shahid Hameed ^a,^*

PMCID: PMC2961752 PMID: 21202885

Abstract

The title compound, C₁₇H₁₆O₅, is an important intermediate for the synthesis of side-chain ligands for polymeric liquid crystals. The propoxy and benzoic acid groups subtend dihedral angles of 4.36 (6) and 55.35 (6)°, respectively, with the central benzoyloxy unit. The crystal structure is stabilized by an intermolecular O—H⋯O hydrogen bond.

Related literature

For related literature, see: Ahmad et al. (2003 ▶); Aranzazu et al. (2006 ▶); Cady et al. (2002 ▶); Hameed & Rama (2004 ▶); Hartung et al. (1997 ▶); Hussain et al. (2003 ▶, 2005 ▶); Kong & Tang (1998 ▶); Nazir et al. (2008a ▶,b ▶); Ribeiro et al. (2008 ▶); Shafiq et al. (2003 ▶, 2005 ▶); Wu & Hsu (2007 ▶); Wu & Lin (2007 ▶).

Experimental

Crystal data

C₁₇H₁₆O₅
M _r = 300.30
Monoclinic,
a = 21.063 (15) Å
b = 5.703 (4) Å
c = 24.437 (18) Å
β = 99.790 (9)°
V = 2893 (3) Å³
Z = 8
Mo Kα radiation
μ = 0.10 mm⁻¹
T = 123 (2) K
0.30 × 0.19 × 0.15 mm

Data collection

Rigaku/MSC Mercury CCD diffractometer
Absorption correction: empirical (NUMABS; Higashi, 1999 ▶) T _min = 0.970, T _max = 0.985
11426 measured reflections
3297 independent reflections
2824 reflections with I > 2σ(I)
R _int = 0.051

Refinement

R[F ² > 2σ(F ²)] = 0.084
wR(F ²) = 0.146
S = 1.26
3297 reflections
201 parameters
H-atom parameters constrained
Δρ_max = 0.29 e Å⁻³
Δρ_min = −0.28 e Å⁻³

Data collection: CrystalClear (Molecular Structure Corporation & Rigaku, 2001 ▶); cell refinement: CrystalClear; data reduction: TEXSAN (Molecular Structure Corporation & Rigaku, 2004 ▶); program(s) used to solve structure: SIR97 (Altomare et al., 1999 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEPII (Johnson, 1976 ▶); software used to prepare material for publication: SHELXL97 and TEXSAN.

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536808016942/hg2407sup1.cif

e-64-o1251-sup1.cif^{(18.2KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808016942/hg2407Isup2.hkl

e-64-o1251-Isup2.hkl^{(161.8KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O3—H3O⋯O4ⁱ	0.84	1.77	2.606 (3)	172

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Symmetry code: (i) Inline graphic .

Acknowledgments

MKR is grateful to The Higher Education Commission of Pakistan for financial support under the International Support initiative program for Doctoral Fellowships in Gifu University, Japan.

supplementary crystallographic information

Comment

Differently substituted aromatic carboxylic acids having benzene rings either joined directly through a covalent bond (Wu & Hsu 2007) or through some functional group, mostly an ester (Cady et al., 2002; Wu & Lin 2007) or an olefin (Nazir et al., 2008a; 2008b), have been investigated for their liquid crystal properties. Such acids have been used in the synthesis of intermediates for side-chain liquid crystal polymers (Kong & Tang 1998) as well as for main-chain liquid crystal polymers (Aranzazu et al., 2006). In addition, the carboxylic acids, in general, have been used as intermediates in the synthesis of a large number of organic compounds (Hussain et al., 2005; 2003; Shafiq et al., 2005; 2003; Ahmad et al., 2003). The pharmaceutical industry has also benefited from this class of compounds (Ribeiro et al., 2008; Hameed & Rama, 2004). The title compound (I) was synthesized in our lab as an intermediate in the synthesis of side-chain liquid crystal polymers, by treating 4-hydroxybenzaldehyde with 4-propyloxybenzoylchloride followed by KMnO₄ oxidation. In this report, the crystal structure of (I) is presented. Bond lengths and angles are within the normal ranges as given for benzoyloxybenzoic acids (Hartung et al., 1997). The C(14)—O(4), C(14)—O(3),C(7)—O(1) and C(7)—O(2) bond lengths are 1.237 (3), 1.300 (3), 1.204 (3) and 1.367 (3) respectively, clearly indicating the partial double bond character of the carboxylate groups. The benzoic acid groups subtend dihedral angles [55.35 (6)°] with the central benzoyloxy moiety C(1)/C(2)/C(3)/C(4)/C(5)/C(6)/C(7)/O(1)/O(2). Two molecules related by an inversion center form a dimer via two hydrogen bonds composed of two carboxyl groups as shown in Fig. 2.

Experimental

To a solution of 4-hydroxybenzaldehyde (0.032 moles) in 50 ml of triethylamine (TEA) was added an equivalent amount of 4-propoxybenzoylchloride with stirring and the mixture heated at 333 K for 1 hour. The excess TEA was removed in vacuo and the product, after recrystallization from hot ethanol, was subjected to KMnO₄ oxidation. The 4-(4-propoxybenzoyloxy)benzaldehyde (0.025 moles) was dissolved in acetone (100 ml) and aqueous KMnO₄ (0.025 moles) was added dropwise at room temperature with stirring. The stirring was continued for three hours when the reaction mixture was filtered and the filtrate acidified using 6M HCl. The product was purified by recrystallization from acetone. Yield: 93% (from 4-(4-propoxybenzoyloxy)benzaldehyde); m.p: 478-480.5K; IR (ν_max, KBr, cm^-1): 3100-2400, 1731, 1685, 1603, 1512, 1425, 1300, 1260, 1206, 1163, 1061, 1009, 758; ¹H-NMR (300 MHz,DMSO-d₆): δ 0.99 (3H, t, J = 7.2 Hz), 1.77 (2H, sex, J = 6.9 Hz), 4.05 (2H, t, J = 6.6 Hz),7.12 (2H, d, J = 8.7 Hz), 7.4 (2H, d, J = 8.7 Hz), 8.03 (2H, d, J = 8.7 Hz),8.08 (2H, d, J = 8.7 Hz), 13.02 (1H, bs); ¹³C-NMR (75 MHz, DMSO-d₆): 10.75, 22.33, 69.91, 115.16, 120.85, 122.70, 128.79, 131.35, 132.60, 154.65, 163.82, 164.29, 167.12.