(Z)-2-Hydroxy-3-(4-methoxyphenyl)acrylic acid

In the structure of the title compound, C10H10O4, inversion dimers linked by pairs of O—H⋯O hydrogen bonds link the carboxylic acid groups. Further O—H⋯O links cross-link the dimers into sheets running along the b-axis direction.

In the structure of the title compound, C 10 H 10 O 4 , inversion dimers linked by pairs of O-HÁ Á ÁO hydrogen bonds link the carboxylic acid groups. Further O-HÁ Á ÁO links cross-link the dimers into sheets running along the b-axis direction.

Related literature
For 3-phenylacrylic acid as intermediates for compounds with biological activity, see: Chen et al. (1993); Igarashi et al. (1997); Xiao et al. (2007); Yu et al. (1991). The title compound was synthesized during the course of our work on the synthesis of potential anticancer compounds, see: Xiao et al. (2008a,b Table 1 Hydrogen-bond geometry (Å , ).

Comment
Derivatives of 3-phenylacrylic acid are key intermediates for tanshinol (Yu et al. 1991), resormycin (Igarashi et al. 1997;Xiao et al. 2007) and benzylazauracil (Chen et al. 1993), which show anti-platelet aggregation, antifungal and antiviral activities, respectively. In the course of our work on screening for anticancers (Xiao, et al. 2008a;Xiao, et al. 2008b), we synthesized the title compound and herein reported its crystal structure.
In the title compound (I), (Z)-2-hydroxy-3-(4-methoxyphenyl)acrylic acid, the plane of benzene ring (with mean dieviation deviation of 0.0053 Å) and the plane of hydroxy acrylic moiety (with mean deviation of 0.0049 Å) make a dihedral angle of 18.001 (97) Å. The benzene ring and the carboxy group occur on opposite side of the C8═C9 double bond with torsion angle of 179.8 (4) ° (Fig. 1). The molecules are linked into dimers by the intermolecular hydrogen bonds occurring the carboxylic acid groups, which lie on crystallographic centres of inversion. These dimers are further cross-linked by intermolecular hydrogen bonds between enolic hydroxy groups and carboxylic acid groups to form sheets running parallel to the crystallographic b axis direction (Table 1 and Fig. 2).
The resulting mixture was allowed to cool to room temperature and the resulting precipitate was collected by filtration.
The crude product was dissolved in EtOAc and twofold volume of petroleum was added carefully. Colorless blocks of (I) suitable for single-crystal structure determination was furnished after 2 d.

Refinement
All H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms with C-H of 0.93 Å for the aromatic H atoms and CH groups, 0.96 Å for the CH 3 groups and with O-H of 0.82 Å for the OH groups.
U iso (H) values were set at 1.2 times U eq (C) for aromatic C groups, 1.5 times U eq (C) for CH 3 , 1.2 times U eq (O) for enolic O-H groups and 1.5 times U eq (O) for carboxylic O-H groups.  bsorption correction: multi-scan (SADABS; Sheldrick, 1996) h = −8→8 Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.