4-Chloro-N-(2,5-dimethylphenyl)benzenesulfonamide

The title compound, C14H14ClNO2S, contains two molecules in the asymmetric unit with different conformations. The C—SO2—NH—C torsion angles are 65.3 (2) and 54.6 (2)° and the aromatic rings are tilted relative to each other by 59.3 (1) and 45.8 (1)° in the two molecules. In the crystal, inversion symmetry results in dimers linked by pairs of N—H⋯O hydrogen bonds for both molecules.

The title compound, C 14 H 14 ClNO 2 S, contains two molecules in the asymmetric unit with different conformations. The C-SO 2 -NH-C torsion angles are 65.3 (2) and 54.6 (2) and the aromatic rings are tilted relative to each other by 59.3 (1) and 45.8 (1) in the two molecules. In the crystal, inversion symmetry results in dimers linked by pairs of N-HÁ Á ÁO hydrogen bonds for both molecules.
KS thanks the University Grants Commission, Government of India, New Delhi, for the award of a research fellowship under its faculty improvement program.
in the present work, the crystal structure of 4-chloro-N-(2,5-dimethylphenyl)benzenesulfonamide (I) has been determined (Fig. 1). The asymmetric unit contains two independent molecules. In one of the molecules, the N-C bond in the C-SO 2 -NH-C segment has gauche torsions with respect to the S═O bonds. The molecules are twisted at the S atoms In the crystal structure, inversion related molecules are linked by N-H···O hydrogen bonding into dimeric aggregates (Table 1 and Fig. 2).

Experimental
A solution of chlorobenzene (10 ml) in chloroform (40 ml) was treated drop wise with chlorosulfonic acid (25 ml) at 273 K. 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 a stoichiometric amount of 2,5-dimethylaniline and boiled for 10 minutes. The reaction mixture was then cooled to room temperature and added to ice-cold water (100 ml). The resultant 4-chloro-N-(2,5-dimethylphenyl)benzenesulfonamide (I) was filtered under suction and washed thoroughly with cold water. It was then recrystallized to constant melting point from aqueous ethanol. Light-brown prisms of (I) were grown from its ethanolic solution by slow evaporation at room temperature.

Refinement
The NH H-atoms were located in a difference map and were refined with the N-H distance restrained to 0.86 (2) Å. The other H atoms were positioned with idealized geometry using a riding model with the aromatic C-H = 0.93 Å and the methyl C-H = 0.96 Å. All H atoms were refined with isotropic displacement parameters set to 1.2U eq of the parent atom.  Fig. 1. The molecular structure of (I), showing the atom-labelling scheme and displacement ellipsoids drawn at the 50% probability level.