Crystal structures of 4-methoxy-N-(4-methylphenyl)benzenesulfonamide and N-(4-fluorophenyl)-4-methoxybenzenesulfonamide

In the crystal structures of 4-methoxy-N-(4-methylphenyl)benzenesulfonamide and N-(4-fluorophenyl)-4-methoxybenzenesulfonamide, the supramolecular architecture of the former is controlled by C—H⋯πaryl interactions, forming a two-dimensional architecture, while in the latter, a pair of C—H⋯O intermolecular interactions lead to the formation of a three-dimensional architecture.


Chemical context
Sulfonamide drugs were the first among the chemotherapeutic agents to be used for curing and preventing bacterial infection in human beings (Shiva Prasad et al., 2011). They play a vital role as a key constituent in a number of biologically active molecules. Up to now, sulfonamides have been known to exhibit a wide variety of biological activities, such as antibacterial (Subhakara Reddy et al., 2012;Himel et al., 1971), antifungal (Hanafy et al., 2007), antiinflamatory (Kuçukguzel et al., 2013), antitumor , anticancer (Mansour et al., 2011), anti-HIV (Sahu et al., 2007) and antitubercular activities (Vora & Mehta, 2012). In recent years, extensive research studies have been carried out on the synthesis and evaluation of pharmacological activities of molecules containing the sulfonamide moiety for different activities, and have been reported to be important pharmacophores (Mohan et al., 2013).

Structural commentary
In (I) (Fig. 1), the benzenesulfonamide ring is disordered due to rotation across the C ar -S(O 2 ) bond over two orientations, ISSN 2056-9890 with atoms C2, C3, C5 and C6 occupying two positions with a 0.516 (7):0.484 (7) ratio. The dihedral angle between the two parts of disordered benzene ring, i.e. C1/C2A/C3A/C4/C5A/ C6A and C1/C2B/C3B/C4/C5B/C6B, is 28.0 (1) . The dihedral angle between the sulfonyl benzene ring (considering the major component) and the aniline ring is 63.36 (19) , and the N-C bond in the C-SO 2 -NH-C segment has a gauche torsion with respect to the S O bonds. Further, the molecule is twisted at the S-N bond, with a C1-S1-N1-C7 torsion angle of 66.33 (19) . The methoxy group in the sulfonylbenzene ring is in the same plane as that of the major component of the disordered sulfonylbenzene ring, the torsion angle C5A-C4-O3-C14 being À176.2 (4) , while it deviates slightly from planarity with respect to the minor component, the C5B-C4-O3-C14 torsion angle being 165.9 (4) .
In (II) (Fig. 2), the dihedral angle between the two benzene rings of 44.26 (13) is less than that observed in (I), and the N-C bond in the C-SO 2 -NH-C segment has a gauche torsion with respect to the S O bonds. Further, the molecule is twisted at the S-N bond, with a C1-S1-N1-C7 torsion angle of 68.4 (2) . Similar to (I), the methoxy group in the sulfonylbenzene ring is in the same plane as that of the sulfonylbenzene ring, the C5-C4-O3-C13 torsion angle being 177.0 (2) .

Supramolecular features
In the crystal structure of (I), N1-H1Á Á ÁO2 hydrogen bonds (Table 1)  A view of (I), showing the atom labelling. Displacement ellipsoids are drawn at the 50% probability level. Only the major component of the disordered benzene ring is shown.

Figure 2
A view of (II), showing the atom labelling. Displacement ellipsoids are drawn at the 50% probability level. Table 1 Hydrogen-bond geometry (Å , ) for (I).

Figure 3
A portion of the crystal packing of (I), viewed approximately along [010] and showing intermolecular hydrogen bonds as thin blue lines. Only the major component of the disordered benzene ring is shown. H atoms not involved in hydrogen bonding have been omitted for clarity.

Figure 4
An N-HÁ Á ÁO hydrogen-bonded (thin blue lines) chain of molecules in the crystal structure of (II).
C1-S1-N1-C7 torsion angles of À72.9 (1), 66.2 (1) and 72.5 (1) , respectively. These values are similar to those observed in (I) and (II). Comparison of the crystal structures (I) and (V) shows that the effect of introducing an electron-donating substituent into the para position of the aniline ring of (I) is quite different than that due to electron-withdrawing substituents. The crystal structure of (III) features N-HÁ Á ÁO hydrogen bonds that form C(4) chains, and thus, the supramolecular architecture is one-dimensional. In (IV), one N-HÁ Á ÁO hydrogen bond and two alternating C-HÁ Á Á aryl (centroid of aniline ring) interactions direct a two-dimensional architecture. This is quite similar to the crystal structure of (I). Thus, the methyl and methoxy groups on the aniline ring have similar influence on the crystal structures of these compounds. However, the crystal structures of (II) and (V) are very different. The crystal structure of (V) features N-HÁ Á ÁO hydrogen bonds that form C(4) chains. Further, (V) does not feature any structuredirecting intermolecular interactions, and thus, the structure is one-dimensional. In contrast to this, the crystal structure of (II) features an N-HÁ Á ÁO and two C-HÁ Á ÁO interactions, leading to a three-dimensional architecture. Thus, the Cl and F atoms on the aniline ring have very different influences on the crystal structures of these compounds.

Synthesis and crystallization
Compounds (I) and (II) were prepared according to the literature method of Vinola et al. (2015). The purity of the compounds were checked by determining the melting points. Single crystals used for X-ray diffraction studies were obtained by slow evaporation of ethanol solutions of the compounds at room temperature.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. The amino H atoms were located in a difference map and were refined isotropically with the bond-length restraint N-H = 0.90 (1) Å . To improve considerably the values of R1, wR2, and S (goodness-of-fit), a partially obscured reflection (i.e. 100) was omitted from the final refinement of (I). The two parts (A and B) of the disordered benzenesulfonyl ring in (I) were restrained to be planar (FLAT instruction), and thus, the r.m.s. deviations (considering non-H atoms) observed for the planes defining the two rings are 0.047 (1) (major-component ring A) and 0.054 (1) Å (minor-component ring B). The disordered atoms (C2, C3, C5 and C6) in both components were isotropically refined, and the C-C bond lengths were restrained to 1.391 (1) Å . For both compounds, data collection: APEX2 (Bruker, 2009); cell refinement: APEX2 and SAINT-Plus (Bruker, 2009); data reduction: SAINT-Plus and XPREP (Bruker, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008). 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 cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'s involving l.s. planes. 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 R-factors(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.  (16) C6A-C1-C2B 113.9 (3) O1-S1-O2 120.18 (10) C6B-C1-C2B 120.3 (3) O1-S1-N1 105.25 (10) C6A-C1-C2A 119.3 (3) O2-S1-N1 107.39 (9) C6B-C1-C2A 116.1 (3) O1-S1-C1 107.99 (10) C6A-C1-S1

Hydrogen-bond geometry (Å, º)
Cg is the centroid of the C7-C12 ring.  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.30 e Å −3 Δρ min = −0.35 e Å −3 Absolute structure: Flack (1983), 973 Friedel pairs Absolute structure parameter: 0.08 (2) 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 cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'s involving l.s. planes. 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 R-factors(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.