N-{4-[(3,4-Dimethylphenyl)sulfamoyl]phenyl}acetamide

Two independent molecules comprise the asymmetric unit of the title compound, C16H18N2O3S. Small but significant twists about the (S)N—C and S—C bonds differentiate the molecules but the most obvious difference is found in the relative orientation of the meta-methyl groups, which lie on opposite sides of the molecules. Overall, both molecules adopt a U shape but with significant twisting evident, particularly in the second independent molecule [dihedral angles between benzene rings = 63.90 (13) and 35.78 (11)°]. In the crystal, N—H⋯O hydrogen bonds lead to supramolecular chains with a tubular topology propagating in [100] and C—H⋯O contacts cross-link the chains.

Two independent molecules comprise the asymmetric unit of the title compound, C 16 H 18 N 2 O 3 S. Small but significant twists about the (S)N-C and S-C bonds differentiate the molecules but the most obvious difference is found in the relative orientation of the meta-methyl groups, which lie on opposite sides of the molecules. Overall, both molecules adopt a U shape but with significant twisting evident, particularly in the second independent molecule [dihedral angles between benzene rings = 63.90 (13) and 35.78 (11) ]. In the crystal, N-HÁ Á ÁO hydrogen bonds lead to supramolecular chains with a tubular topology propagating in [100] and C-HÁ Á ÁO contacts cross-link the chains.
Two independent molecules comprise the crystallographic asymmetric unit of (I). There are non-chemically significant differences between the two molecules with the first, Fig. 1, being almost super-imposable upon the second, Fig. 2, but with twists evident about the (S)N-C and S-C bonds, Fig. 3. About the former, the differences are quantified in the S1-N1-C1-C2 and S2-N3-C17-C22 torsion angles of -107.5 (2) and -93.8 (2) °, respectively. About the S-C bond, the twists are evident in the O1-S1-C9-C10 and O4-S2-C25-C26 torsion angles of -44.3 (2) and -25.36 (19) °, respectively. In each case, the acetamide group is co-planar with the benzene ring to which it is bonded [C12-N2-C15-O3 = 0.5 (4) ° and C28-N4-C31-O6 = -3.2 (4) °]. The major difference relates to the relative disposition of the meta-methyl group which effectively resides on opposite sides in the two molecules, Fig. 3. Within each molecule, the benzene molecules are orientated in the same direction and form dihedral angles of 63.90 (13) ° (first molecule) and 35.78 (11) ° so that overall the molecules have a U-shaped but with significant twisting, in particular for the second independent molecule.
The crystal packing is dominated by N-H···O hydrogen bonds whereby each of the amide-N atoms forms an interaction with a sulfamoyl-O atom, Table 1. The sulfamoyl-N-H forms an interaction with an amide-O in the case of N1 but with a sulfamoyl-O atom in the case of N4, Table 1. The result of the hydrogen bonding is the formation of a supramolecular chain along the a axis with a tubular topology, Fig. 4. Perhaps surprisingly, the hydrogen bonding scheme does not involve the amide-O6 atom, which lies to the periphery of the chain, Fig. 4. However, the O6 atom forms a very short intramolecular C-H···O contact [H···O = 2.22 Å] and forms three further C-H···O contacts less than 2.72 Å [shortest = 2.65 Å with H16c i where i: x, -1 + y, z], thereby providing links between the supramolecular chains.

Experimental
To 3,4-dimethyl aniline (242 mg, 2 mmol) in distilled water (10 ml) was added 4-acetamido benzene sulfonyl chloride (467 mg, 2 mmol) with stirring at room temperature while maintaining the pH of the reaction mixture at pH 8 using 3% sodium carbonate. The progress of the reaction was monitored by TLC. The precipitate formed was washed with water, dried and crystallized from a methanol/ethyl acetate mixture (50:50 V/V) to yield light-orange blocks of (I).

Special details
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The 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 > 2σ(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.