4-Hydroxyanilinium 2-chloroacetate

In the crystal of the title salt, C6H8NO+·C2H2ClO2 −, the 4-hydroxyanilinium cation links to adjacent chloroacetate anions via N—H⋯O and O—H⋯O hydrogen bonds; weak C—H⋯O interactions also occur between the anions and cations.

In the crystal of the title salt, C 6 H 8 NO + ÁC 2 H 2 ClO 2 À , the 4hydroxyanilinium cation links to adjacent chloroacetate anions via N-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonds; weak C-HÁ Á ÁO interactions also occur between the anions and cations.

Comment
Simple organic salts containing strong intrermolecular H-bonds have attracted an attention as materials which display ferroelectric-paraelectric phase transitions Huang et al., 1999;Zhang et al., 2001). With the purpose of obtaining phase transition crystals of organic salts, various organic molecules have been studied and a series of new crystal materials have been elaborated (Wang et al., 2002;Xue et al., 2002;Ye et al., 2008). Herewith, we present the synthesis and crystal structure of the title compound, 4-hydroxyanilinium 2-chloroacetate.
In the title compound (

Experimental
The 2-chloroacetic acid (10 mmol), 4-aminophenol (10 mmol) and ethanol (50 mL) were added into a 100 mL flask. The mixture was stirred at 333 K for 2 h, and then the precipitate was filtered out. Colourless crystals suitable for X-ray diffraction were obtained by slow evaporation of the solution.

Refinement
All the H atoms attached to C atoms were situated into the idealized positions and treated as riding with C-H = 0.95 Å (aromatic) and C-H = 0.99 Å (methylene) with U iso (H) = 1.2U eq (C). The positional parameters of the H atoms bonded to N and O were located in a difference Fourier map and refined with restraints of H-N = 0.91 (2) and H-O = 0.82 (2) Å,

Computing details
Data collection: CrystalClear (Rigaku, 2005); cell refinement: CrystalClear (Rigaku, 2005); data reduction: CrystalClear (Rigaku, 2005); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure:  A view of the asymmetric unit with the atomic numbering scheme. The displacement ellipsoids were drawn at the 30% probability level. Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. 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 > 2sigma(F 2 ) is used only for calculating R-factors(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.