4-Chloro-N-phenylbenzenesulfonamide

In the crystal of the title compound, C12H10ClNO2S, the asymmetric unit contains two independent molecules. The N—C bonds in the C—SO2—NH—C segments have gauche torsions with respect to the S=O bonds. The molecules are twisted at the S atoms with C—SO2—NH—C torsion angles of −53.8 (3) and −63.4 (3)° in the two molecules. The benzene rings are tilted relative to each other by 69.1 (1) and 82.6 (1)°. The dihedral angle between the sulfonyl benzene rings of the two independent molecules is 23.7 (2)°. The crystal structure features inversion-related dimers linked by N—H⋯O hydrogen bonds.

In the crystal of the title compound, C 12 H 10 ClNO 2 S, the asymmetric unit contains two independent molecules. The N-C bonds in the C-SO 2 -NH-C segments have gauche torsions with respect to the S O bonds. The molecules are twisted at the S atoms with C-SO 2 -NH-C torsion angles of À53.8 (3) and À63.4 (3) in the two molecules. The benzene rings are tilted relative to each other by 69.1 (1) and 82.6 (1) . The dihedral angle between the sulfonyl benzene rings of the two independent molecules is 23.7 (2) . The crystal structure features inversion-related dimers linked by N-HÁ Á ÁO hydrogen bonds.
KS thanks the University Grants Commission, Government of India, New Delhi, for the award of a research fellowship under its faculty improvement program.

Comment
The sulfonamide moieties are the constituents of many biologically important compounds. The hydrogen bonding preferences of sulfonamides has been investigated (Adsmond & Grant, 2001). As a part of studying the substituent effects on the structures and other aspects of this class of compounds (Gowda, & Kumar, 2003;Gowda et al., 2004;Shakuntala et al., 2011a,b), in the present work, the crystal structure of 4-chloro-N-(phenyl)-benzenesulfonamide (I) has been determined ( Fig.1). The asymmetric unit of the structure contains two independent molecules. The N-C bonds in the The sulfonyl and the anilino benzene rings in the two independent molecules of (I) are tilted relative to each other by 69.1 (1)° in molecule 1, and 82.6 (1)° in molecule 2, compared to the values of 84.7 (1)° in (II) and 77.1 (1)° in (III).
In the crystal structure of the title compound the molecules are linked by N-H···O(S) hydrogen bonding into dimers that are located on centers of inversion (Table 1 and Fig.2).

Experimental
The solution of chlorobenzene (10 ml) in chloroform (40 ml) was treated dropwise with chlorosulfonic acid (25 ml) at 0° C. After the initial evolution of hydrogen chloride subsided, the reaction mixture was brought to room temperature and poured into crushed ice in a beaker. The chloroform layer was separated, washed with cold water and allowed to evaporate slowly. The residual 4-chlorobenzenesulfonylchloride was treated with aniline in the stoichiometric ratio and boiled for ten minutes. The reaction mixture was then cooled to room temperature and added to ice cold water (100 ml). The resultant 4-chloro-N-(phenyl)-benzenesulfonamide was filtered under suction and washed thoroughly with cold water. It was then recrystallized to constant melting point from dilute ethanol. The compound was characterized by recording its infrared and NMR spectra.
Prism like colorless single crystals used in X-ray diffraction studies were grown in ethanolic solution by slow evaporation at room temperature.

Refinement
The H atoms of the NH groups were located in a difference map and later restrained to the distance N-H = 0.86 (2) Å.
The other H atoms were positioned with idealized geometry with C-H = 0.93 Å and refined isotropic with U iso (H) = 1.2 U eq (C) using a riding model.   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.