Butyl 4-(4-methylbenzenesulfonamido)benzoate

In the title compound, C18H21NO4S, the aromatic rings are almost normal to each other, with a dihedral angle of 89.27 (18)°. The molecular conformation is stabilized by an intramolecular C—H⋯O interaction, which generates an S(6) motif. In the crystal, N—H⋯O and C—H⋯O hydrogen bonds lead to the formation of chains propagating along [010]. Neighbouring chains are linked via a C—H⋯π interaction. The –CH2CH2CH3 atoms of the butyl group are disordered over two sets of sites, with a refined site-occupancy ratio of 0.536 (16):0.464 (16).

In the title compound, C 18 H 21 NO 4 S, the aromatic rings are almost normal to each other, with a dihedral angle of 89.27 (18) . The molecular conformation is stabilized by an intramolecular C-HÁ Á ÁO interaction, which generates an S(6) motif. In the crystal, N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds lead to the formation of chains propagating along [010]. Neighbouring chains are linked via a C-HÁ Á Á interaction. The -CH 2 CH 2 CH 3 atoms of the butyl group are disordered over two sets of sites, with a refined site-occupancy ratio of 0.536 (16):0.464 (16).
Cg1 is the centroid of the C2-C7 benzene ring. As part of our ongoing studies of sulfonamides with potential biological properties (Mustafa et al., 2010(Mustafa et al., , 2011(Mustafa et al., , 2012Khan et al., 2011), we describe herein the synthesis and crystal structure of the title compound.
The molecular conformation of the title compound is stabilized by an intramolecular C-H···O interaction, generating an S(6) motif (Table 1; Bernstein et al., 1995). In the crystal, N-H···O and C-H···O hydrogen bonds lead to the formation of chains propagating along [010] -see Fig. 2 and Table 1. Neighbouring chains are linked via a C-H···π interaction (Table 1).

Experimental
To an aquious solution of p-amino benzoic acid (1.0 g, 7.3 mmol), sodium carbonate (1 N) was added to adjust the pH to 8. p-toluenesulfonyl chloride (1.80 g, 9.48 mmol) was then added and the mixture was stirred at room temperature keeping the pH of the mixture up to 8 with occasional addition of sodium carbonate solution. The progress and completion of the reaction was confirmed by TLC and conversion of the suspension into a clear solution. After 2 h, the mixture was poured into a beaker and the pH was adjusted to 2.0 by addition of 1 N HCl. Precipitates were produced which were filtered and washed with distilled water. The prepared sulfonamide (4-(toluene-4-sulfonylamino)-benzoic acid) (1.0 g, 3.43 mmol), DMF (10 ml) and n-hexane washed with sodium hydride (0.25 g, 10.31 mmol) were stirred at room temperature for 40 min, followed by the addition of butyl iodide (0.94 g, 5.15 mmol). The whole reaction mixture was stirred till the completion of the reaction and poured into crushed ice in a beaker. The pH of the mixture was adjusted to 4.0 with 1 N HCl. Precipitates were produced, filtered and washed twice with distilled water. Crystallization in chloroform gave long block-like pale-yellow X-ray quality crystals of the title compound.

Refinement
All the H-atoms were included in calculated positions and treated as riding atoms: N-H = 0.88 (2) Å, C-H = 0.93, 0.96 and 0.97 Å for CH, CH 3 and CH 2 H-atoms, respectively, with U iso (H) = k × U eq (N,C), where k = 1.5 for CH 3 H-atoms and    Table 1 for details). Only the atoms of the major disordered component of the terminal butyl group are shown. Special details Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles Refinement. Refinement on F 2 for ALL reflections except those flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses 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 observed criterion of F 2 > σ(F 2 ) is used only for calculating -R-factor-obs 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.