2-(3-Oxo-2,3-dihydro-1,2-benzothiazol-2-yl)acetic acid

In the title compound, C9H7NO3S, the benzoisothiazolone ring system is essentially planar, with a maximum deviation of 0.013 (2) Å. In the crystal, molecules are linked via O—H⋯O hydrogen bonds, forming chains along [010]. In addition, weak intermolecular C—H⋯O hydrogen bonds are present.

In the title compound, C 9 H 7 NO 3 S, the benzoisothiazolone ring system is essentially planar, with a maximum deviation of 0.013 (2) Å . In the crystal, molecules are linked via O-HÁ Á ÁO hydrogen bonds, forming chains along [010]. In addition, weak intermolecular C-HÁ Á ÁO hydrogen bonds are present.

Structure Reports Online
The molecular structure of the title compound (I) is shown in Fig. 1. Examples of related structures appear in the literature (Xu, et al., 2006;Wang, et al., 2011a,b,c). In (I) the benzoisothiazolone ring system is essentially planar, with a maximum deviation of 0.013 (2) Å. In the crystal, molecules are linked via O-H···O hydrogen bonds to form one-dimensional chains along [010]. In addition weak intermolecular C-H···O hydrogen bonds are present.

Experimental
Chloroactic acid (0.95 g, 0.01 mol) was added dropwise to a solution of sodium hydroxide (0.80 g, 0.02 mol) and benzo[d]isothiazol-3(2H)-one (1.50 g, 0.01 mol)in water (20 ml) under stirring on an ice-water bath. The reaction mixture was stirred at room temperature for 4.5 h and adjusted pH to 1~2, to afford the title compound (1.05 g, yield 50.0%). Single crystals suitable for X-ray measurements were obtained by recrystallization of the title compound from the mixed solution of dimethyl formamide and water at room temperature.

Refinement
Atom H3O was located from the difference Fourier map and was refined freely [O-H = 0.86 (3) Å]. The remaining H atoms bonded to C atoms were fixed geometrically and allowed to ride on their attached atoms, with the carrier atom-H distances = 0.95 Å for aryl, 0.99 for methylene, and U iso (H) = 1.2U eq (C). Fig. 1. The molecular structure of the title compound with displacement ellipsoids drawn at the 30% probability level. H atoms are presented as a small spheres of arbitrary radius.

Figures
supplementary materials sup-2 Detector resolution: 28.5714 pixels mm -1 θ max = 29.1°, θ min = 3.1°φ and ω scans h = −6→6 Absorption correction: multi-scan (ABSCOR; Higashi, 1995) k = −15→15 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.