5-(4-Methylpiperazin-1-yl)-2-nitroaniline

In the title compound, C11H16N4O2, the dihedral angle between the benzene ring and the plane of the four carbon atoms in the piperazine ring is 12.17 (3)°; the latter ring adopts a chair conformation. An intramolecular N—H⋯O hydrogen bond generates an S(6) ring. In the crystal, the molecules are linked by N—H⋯N hydrogen bonds, forming chains.

In the title compound, C 11 H 16 N 4 O 2 , the dihedral angle between the benzene ring and the plane of the four carbon atoms in the piperazine ring is 12.17 (3) ; the latter ring adopts a chair conformation.

Related literature
By contrast, due to the piperazine moiety adopting a chair conformation N1-C2-C5 and N2-C3-C4 form two separate planes with torsion angle of 45.87 (2) ° and 25.92 (3) °, respectively, with respect to the benzene ring. The crystal structure of the title compound exhibits N-H···O, C-H···O, and N-H···N intra-and intermolecular hydrogen bonds to form a three dimensional network.
As can be seen from the packing diagram, (Fig. 2), the molecules are stacked along the b axis.

Experimental
The title compound, (I) was prepared by a literature method (Renhowe, P. A. et al., 2009). Crystals suitable for X-ray analysis were obtained by dissolving (I) (0.5 g) in methanol (20 ml) and evaporating the solvent slowly at room temperature for about 7 d.

Refinement
H atoms were positioned geometrically, with N-H = 0.86 Å, C-H = 0.93 Å for aromatic H, 0.97 Å for methylene and 0.96 Å for methyl groups. Refinement was performed using a riding model with U iso (H) = xU eq (C), where x = 1.5 for methyl and x = 1.2 for all other H atoms. Fig. 1. The molecular structure of (I), with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.

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 > 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.