4-Nitrophthalamide

In the title compound, C8H7N3O4 (systematic name: 4-nitrobenzene-1,2-dicarboxamide), each of the substituents is twisted out of the plane of the benzene ring to which it is attached [dihedral angles of 11.36 (2)° for the nitro group, and 60.89 (6) and 34.39 (6)° for the amide groups]. The amide groups are orientated to either side of the least-squares plane through the benzene ring with the amine groups being directed furthest apart. In the crystal, a three-dimensional architecture is established by a network of N—H⋯O hydrogen bonds.

In the title compound, C 8 H 7 N 3 O 4 (systematic name: 4-nitrobenzene-1,2-dicarboxamide), each of the substituents is twisted out of the plane of the benzene ring to which it is attached [dihedral angles of 11.36 (2) for the nitro group, and 60.89 (6) and 34.39 (6) for the amide groups]. The amide groups are orientated to either side of the least-squares plane through the benzene ring with the amine groups being directed furthest apart. In the crystal, a three-dimensional architecture is established by a network of N-HÁ Á ÁO hydrogen bonds.

Structural commentary
As part of our on-going study of functional phthalocyanines, we have previously reported the synthesis and structure of 4-(prop-2-ylnyloxy)phthalonitrile, prepared from 4-nitrophthalonitrile (Chin et al. (2012). The latter, in turn, is prepared by dehydration of the title compound. As the structure of the title compound is not reported, herein its crystal structure determination is described.
In the title compound, Fig. 1 side of the benzene ring, with the amine groups similarly orientated but directed away from each other. As such, there are no intramolecular hydrogen bonding contacts. Very similar conformations were found for the two independent molecules comprising the asymmetric unit of the 1,2-dicarboxamide parent compound (Hamada et al., 2012).
In the crystal packing, each N-H H atoms forms a N-H···O hydrogen bond with H31 being bifurcated (Table 1); both O1 and O3 accept two hydrogen bonds. The result is a three-dimensional architecture that can be described globally as comprising columns of molecules aligned along the a axis (Fig. 2).

Synthesis and crystallization
The title compound was prepared by modification of a literature procedure (Rasmussen et al., 1978). 4-Nitrophthalimide and concentrated NH 4 OH were stirred at room temperature for 24 h. The precipitate (an off-white powder) was filtered under vacuum and washed with cold water to provide the title compound in 0.68 g yield (63.8 %). M.pt: 465-469 K (literature: 462-464 K). Crystals for the X-ray study were grown from slow evaporation of its aqueous solution.

Refinement
All C-bound H atoms were refined freely. The N-H atoms were located from difference map and refined with N-H = 0.88±0.01 Å, and with unrestrained U iso (H).

Figure 1
The molecular structure of the title compound showing the atom-labelling scheme and displacement ellipsoids at the 70% probability level.  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 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.