4-Methyl-2-(2-nitrobenzenesulfonamido)pentanoic acid

In the title compound, C12H16N2O6S, the S atom adopts a distorted tetrahedral geometry with an O—S—O angle of 119.76 (13)°. The nitro group is twisted by 35.34 (2)° with respect to the aromatic ring; it accepts an N—H⋯O hydrogen bond, resulting in a S(7) motif. In the crystal, N—H⋯O and O—H⋯O hydrogen bonds connect the molecules into an infinite chain along the a axis. The methyl C atoms of the isopropyl group are disordered in a 1:1 ratio.

In the title compound, C 12 H 16 N 2 O 6 S, the S atom adopts a distorted tetrahedral geometry with an O-S-O angle of 119.76 (13) . The nitro group is twisted by 35.34 (2) with respect to the aromatic ring; it accepts an N-HÁ Á ÁO hydrogen bond, resulting in a S(7) motif. In the crystal, N-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonds connect the molecules into an infinite chain along the a axis. The methyl C atoms of the isopropyl group are disordered in a 1:1 ratio.

Comment
In order to explore the structural behaviour of sulfonamide derived from amino acids (Arshad et al., 2010), here we report the crystal structure of title compound.
The nitro group attached to aromatic ring is twisted at dihedral angle of 35.34 (2)°, with the maximum deviation from the two oxygen atoms being -0.532 (6) Å for O1 and 0.703 (5) Å for O2. An intramolecular N-H···O leads to the formation of a seven membered ring motif, S 1 1 (7) (Bernstein et al., 1995). The nitro group is oriented at an angle of 29.84 (6)° with respect to aromatic ring. Adjacent molecules are linked to form an infinite chain along a axis through O-H···O and N-H···O interactions (Table. 1, Fig. 2).

Experimental
L-lucine (0.20 g, 0.089 mmole) dissolved in 5-10 mL distilled water was treated with sodium carbonate (1M) to a pH of 8-9. 2-Nitrobenzenesulphonyl chloride (0.117 g, 0.089 mmole) added within 3-5 min. The pH was adjusted by sodium carbonate (1M). Then, dilute HCl was added dropwise to result in a pH 2-3. The precipitate was filtered, washed with plenty of water and dried. Suitable crystals was obtained upon recrystalization in methanol.

Refinement
All the C-H and H-atoms were positioned with idealized geometry with C-H = 0.93 Å for aromatic, C-H = 0.96 Å for methyl group and C-H = 0.97 Å for methylene, and were refined using a riding model with U iso (H) = 1.2 U eq (C) for aromatic and methylene and U iso (H) = 1.5 U eq (C) for methyl carbon atoms.
The N-H = 0.85 (1) and O-H = 0.85 (1) Å hydrogen atoms were located with difference map and were refined with Reaction does not affect the chirality of product, and the chirality is that of the reactant (L-Lucine).
The atoms C7-C11 were disordered over two positions with the occupancies of 0.50 for C7A-C11A and 0.50 for C7B-C11B. , The temperature factors of pairs of atoms were restrained to be identical. The C7a/C7b pair of atoms had the same site.  The labelled molecular structure of (I) with 50% displacement ellipsoids.

Figure 2
Unit cell packing showing hydrogen bonds, drawn using dashed lines. Hydrogen atoms not involved in hydrogen bonding have been omitted.  (10) Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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.