2-Chloro-N-(3-chloro-benzo-yl)benzene-sulfonamide.

The asymmetric unit of the title compound, C(13)H(9)Cl(2)NO(3)S, contains two independent mol-ecules. The conformation of the C=O bond is anti to the meta-Cl group in the chloro-benzoyl group of one of the mol-ecules and syn in the other. The dihedral angles between the sulfonyl and benzoyl benzene rings are 77.8 (1) and 83.5 (1)°. In the crystal structure, two pairs of independent mol-ecules are linked into a tetra-mer by N-H⋯O hydrogen bonds.

The asymmetric unit of the title compound, C 13 H 9 Cl 2 NO 3 S, contains two independent molecules. The conformation of the C O bond is anti to the meta-Cl group in the chlorobenzoyl group of one of the molecules and syn in the other. The dihedral angles between the sulfonyl and benzoyl benzene rings are 77.8 (1) and 83.5 (1) . In the crystal structure, two pairs of independent molecules are linked into a tetramer by N-HÁ Á ÁO hydrogen bonds.

Comment
As a part of studying the effect of ring and the side chain substitutions on the crystal structures of N-aryl sulfonamides (Gowda et al., 2009(Gowda et al., , 2010Suchetan et al., 2010a,b), the structure of 2-chloro-N-(3-chlorobenzoyl)-benzenesulfonamide (I) has been determined. The asymmetric unit of (I) contains two independent molecules. In the C-SO 2 -NH-C(O) segments, the N-H bonds are anti to the C═O bonds ( Fig.1), similar to those observed in 2-chloro-N-(3-methylbenzoyl)-

Experimental
The title compound was prepared by refluxing a mixture of 3-chlorobenzoic acid, 2-chlorobenzenesulfonamide and phosphorous oxy chloride for 3 h on a water bath. The resultant mixture was cooled and poured into ice cold water. The solid obtained was filtered, washed thoroughly with water and then dissolved in sodium bicarbonate solution. The compound was later reprecipitated by acidifying the filtered solution with dilute HCl. It was filtered, dried and recrystallized. Rod like colourless single crystals of the title compound used in X-ray diffraction studies were obtained by a slow evaporation of its toluene solution at room temperature.

Refinement
The H atoms of the NH groups were located in a difference map and refined with the a N-H distance restraint of 0.86 (2) %A. The other H atoms were positioned with idealized geometry using a riding model with C-H = 0.93 Å.
All H atoms were refined with isotropic displacement parameters (set to 1.2 times of the U eq of the parent atom). The residual electron-density features are located in the region of H25 and Cl4. The highest peak is 0.98 Å from H25 and the deepest hole is 0.68 Å from Cl4.  Fig. 1. The two independent molecules of the title compound, showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% 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 > 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.