2-Methylsulfonyl-4-(trifluoromethyl)benzoic acid

In the title molecule, C9H7F3O4S, the S and the methyl C atoms of the methylsulfonyl group deviate from the benzene ring plane by 0.185 (2) and −1.394 (3) Å, respectively. In the crystal, O—H⋯O hydrogen bonds link the molecules into chains along [201]. Weak C—H⋯O interactions further link these chains into layers parallel to the ac plane.

In the title molecule, C 9 H 7 F 3 O 4 S, the S and the methyl C atoms of the methylsulfonyl group deviate from the benzene ring plane by 0.185 (2) and À1.394 (3) Å , respectively. In the crystal, O-HÁ Á ÁO hydrogen bonds link the molecules into chains along [201]. Weak C-HÁ Á ÁO interactions further link these chains into layers parallel to the ac plane.
In (I) (Fig. 1), the S and the methyl C atoms of the methylsulfonyl group deviate from the benzene ring plane at 0.185 (2) and -1.394 (3) Å, respectively. Intermoleculear O-H···O hydrogen bonds (Table 1) (Table 1) link further these chains into layers parallel to ac plane.

Experimental
The title compound was prepared by the reaction of 2-(methylsulphenyl)-4-trifluoromethylbenzoic acid and hydrogen peroxide in acetic acid at 10 ° (Cain et al., 1998). A colourless crystal suitable for single-crystal X-ray diffraction was obtained by the recrystallization from dichloromethane.

Refinement
C-bound H atoms were placed in calculated positions and treated as riding on their parent atoms, with C-H = 0.93 -0.96 Å , and with U iso (H) = 1.2 -1.5 U eq (C). O-bound H atoms were located in a differece Fourier map and were refined with restraint as O-H = 0.82 (1) Å, and U iso (H) = 1.5U eq (O).

Figure 2
A portion of the crystal packing showing hydrogen-bonded (dashed lines) chains.

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.