2-[4-(Carboxymethyl)phenoxy]acetic acid

The title compound, C10H10O5, was obtained by the reaction of 4-hydroxyphenylacetic acid with chloroacetic acid. In the crystal, the molecules form a three-dimensional network by way of intermolecular O—H⋯O hydrogen bonding.

The title compound, C 10 H 10 O 5 , was obtained by the reaction of 4-hydroxyphenylacetic acid with chloroacetic acid. In the crystal, the molecules form a three-dimensional network by way of intermolecular O-HÁ Á ÁO hydrogen bonding.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: DS2074).

Comment
Various aromatic carboxylic acid ligands are being used in designing versatile metal-organic frameworks (MOFs) having potential applications (Kuppler et al., 2009;Jahan et al., 2010;Armelao et al., 2010;Yashima et al., 2009). In present work, we report the synthesis and single crystal structure of a new aromatic dicarboxylic acid ligand namely 4-carboxymethoxy phenylacetic acid (I) containing two flexible carboxylic acid groups, obtained by the reaction of 4-hydroxyphenylacetic (Gracin et al., 2005) and chloroacetic acid (Sandhu et al., 1991).
The molecular structure of the title compound is presented in Fig.1. The carboxymethoxy group is almost parallel to the benzene ring with a dihedral angle of 11.4 (1)° between the two least-squares planes,while the acetic acid unit is almost perpendicular to the benzene ring, making a dihedral angle of 72.4 (2)°.In addtion, the moleculars were linked by the intermolecular O-H···O hydrogen bonding forming a three-dimensional network (Fig.2).

Experimental
The solution of 4-hydroxyphenylacetic acid (1.522 g, 10.0 mmol) in water (10 ml) neutralized with NaOH (0.8 g, 20 mmol) was added to a 1:1 mixture of chloroacetic acid (3.78 g, 40 mmol) and NaOH (1.600 g, 40 mmol) with stirring to adjust the pH value of the mixture to ca 11 and refluxed at 90 0 C for 3 h. The pH value was adjusted to 2-3 with concentrated hydrochloric acid. While cooling the mixture to room temperature, a white precipitate was appeared rapidly. The solid was filtrated, washed by water. Single crystals suitable for X-ray diffraction were obtained in the mother liquid after evaporation within a few days.

Refinement
The Flack parameter could not be refined to an acceptable value as the title compound is a poor anomalous scatterer even after using MOVE command in Shelxl97. Therefore, the Friedel oppostites were merged (using MERG 3 command in