N-(2-Chlorophenylsulfonyl)-2,2-dimethylpropanamide

In the title compound, C11H14ClNO3S, the C—S—N—C torsion angle is −61.69 (17)°. In the crystal, inversion dimers linked by pairs of N—H⋯O hydrogen bonds occur, generating R 2 2(8) loops.

KS thanks the University Grants Commission, Government of India, New Delhi, for the award of a research fellowship under its faculty improvement program.
gen bonding in the solid state, due to the presence of various hydrogen bond donors and acceptors, gives rise to polymorphism (Yang & Guillory, 1972). The hydrogen bonding preferences of sulfonamides has also been investigated (Adsmond & Grant, 2001). The nature and position of substituents in N-(aryl)sulfonoamides play a significant role on their crystal structures. As a part of a study of the substituent effects upon their crystal structures (Gowda et al., 2007(Gowda et al., , 2008Shakuntala et al., 2011a,b), in the present work, the crystal structure of N-(2-chlorophenylsulfonyl)-2,2,2-trimethylacetamide (I) has been determined. The N-H and C═O bonds in the SO 2 -NH-CO-C segment of (I) are anti to each other ( Fig. 1 et al., 2008) and N-(2-chlorophenylsulfonyl)-acetamide (IV) (Shakuntala et al., 2011b). Further, the amide hydrogen is syn to the ortho-chloro group in the benzene ring.
The N-C bond in the C-SO 2 -NH-C segment has gauche torsion with respect to the S═O bonds. The molecule is twisted at the S-atom with a C-S-N-C torsion angle of -61.7 (2) °, compared to the values of -65.4 (2) ° in (II), -64.5 (3) ° in (III), and -71.7 (3) ° and 61.2 (3) ° in the two independent molecules of (IV).
In the crystal structure, the pairs of intermolecular N-H···O hydrogen bonds (Table 1) link the molecules into inversion-related dimers; a view of the crystal packing is shown in Fig. 2.

Experimental
The title compound was prepared by refluxing 2-chlorobenzenesulfonamide (0.10 mole) with an excess of pivalyl chloride (0.20 mole) for about an hour on a water bath. The reaction mixture was cooled and poured into ice cold water. The resulting solid was separated, washed thoroughly with water and dissolved in warm dilute sodium hydrogen carbonate solution. The title compound was re-precipitated by acidifying the filtered solution with glacial acetic acid. It was filtered, dried and recrystallized from ethanol. Colorless prisms of the title compound used in X-ray diffraction studies were obtained from a slow evaporation of an ethanolic solution of the compound.

Refinement
The H atom of the NH group was 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 using a riding model with the aromatic C-H = 0.93 Å and methyl C-H = 0.96 Å. All H atoms were refined with isotropic displacement parameters (set to 1.2 times of the U eq of the parent atom).   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.