2-(Biphenyl-4-yloxy)acetic acid

In the title compound, C14H12O3, the phenyl and benzene rings make a dihedral angle of 47.51 (4)°. In the crystal, molecules are dimerized by double O—H⋯O hydrogen bonds, forming centrosymmetric R 2 2(8) ring motifs. The dimers are interlinked by C—H⋯π interactions into zigzag layers.

In the title compound, C 14 H 12 O 3 , the phenyl and benzene rings make a dihedral angle of 47.51 (4) . In the crystal, molecules are dimerized by double O-HÁ Á ÁO hydrogen bonds, forming centrosymmetric R 2 2 (8) ring motifs. The dimers are interlinked by C-HÁ Á Á interactions into zigzag layers.

Comment
Biphenyl moieties have been found to act as pharmacophores in many biological studies such as antimycobacterial testing (Kamoda et al., 2006). Several derivatives of biphenyl-4-yloxy acetic acid are reported to be potential drugs with anti-inflammatory activity, analgesic activity and lower ulcerogenic potential (Kumar et al., 2008). A series of benzofuran/benzothiophene biphenyl oxo-acetic acids act as potent inhibitors of protein tyrosine phosphatase 1B with good oral antihyperglycemic activity (Malamas et al., 2000). In this paper we report the crystal structure of the title compound, (I).
In the crystal of the title compound ( Fig. 1), two carboxyl groups form a pair of hydrogen bonds in cyclic R 2 2 (8) arrangement (Etter, 1990). The pairs of hydrogen bonds link the molecules into inversion dimers. The dimers are arranged in a herringbone pattern with an angle of 66.15 (1)°. The adjacent dimers are linked via C-H···π interactions with the H···π distance of 2.86 Å (Fig. 2). Some crystal structures containing biphenyl moiety have been reported. The two benzene rings are usually nearly coplanar for the biphenyl compounds without 2-substituents (Ali et al., 2008;Cao, 2009;Margraf et al., 2009;Li et al., 2009;Charbonneau & Delugeard, 1977). But the title compound displays a twisted conformation with a dihedral angle of 47.51 (4)° between the phenyl and benzene planes. Planar conformations will be adopted by biphenyl compounds in the ground states. It is the crystal packing forces that produce the planar conformations for the biphenyl compounds (Brett et al., 1999).

Experimental
The crystals of (biphenyl-4-yloxy)acetic acid were unexpectedly obtained in the preparation of (biphenyl-4-yloxy)acetic acid-β-cyclodextrin inclusion complex. The experiment scheme is as follows: An ethanol solution of (biphenyl-4yloxy)acetic acid (1 mmol, 5 ml) was added dropwise to an aqueous solution of β-cyclodextrin (1 mmol, 50 ml) and stirred at 50 °C for 6 h. The resulting solution was filtered and then stored at 40 °C. Colorless crystals suitable for the single X-ray diffraction were obtained after one week.

Refinement
H atoms bonded to C were positioned geometrically with aromatic C-H = 0.93 Å and aliphatic C-H = 0.97 Å. Their displacement parameters were set at U iso (H) = 1.2U eq (C). The hydroxyl H atom was found in a Fourier map and refined with the constraint of O-H = 0.82 Å, U iso (H) = 1.2U eq (O). Fig. 1. Molecular configuration and atom numbering scheme for the title compound, with displacement ellipsoids drawn at the 50% probability level.