Crystal structure of 2,3-dimethoxy-N-(4-nitrophenyl)benzamide

In the crystal, intermolecular weak C—H⋯O hydrogen bonds link the molecules into the supramolecular chains propagating along the a axis.

In the title compound, C 15 H 14 N 2 O 5 , the benzene rings are nearly coplanar, making a dihedral angle of 4.89 (8) . An intramolecular N-HÁ Á ÁO hydrogen bond occurs between the imino and methoxy groups. In the crystal, weak C-HÁ Á ÁO hydrogen bonds link the molecules into supramolecular chains propagating along the a-axis direction.stacking is observed between parallel benzene rings of neighbouring chains, the centroid-to-centroid distance being 3.6491 (10) Å . Three-dimensional Hirshfeld surface analyses and twodimensional fingerprint plots have been used to analyse the intermolecular interactions present in the crystal.

Chemical context
Amides have a very important place in both organic and biological chemistry. They are used as building blocks for natural products such as proteins and peptides. However, amides are not restricted to biological systems, but also have a wide range of uses in pharmaceutical chemistry (Khalafi-Nezhad et al., 2005;Valeur & Bradley, 2009). Many amide derivatives have been found to possess antitumor, antimicrobial, anti-HIV, anti-inflammatory, anticonvulsant, antibacterial, antifungal, analgesic and anticancer properties (Kushwaha et al., 2011;Fu et al., 2010;Carbonnelle et al., 2005;Siddiqui et al., 2008). Benzamides and their derivatives are compounds of biological and pharmaceutical importance. A variety of benzamide derivatives have been synthesized by the interaction of aniline derivatives that carry electron-donating groups (anisidines, toluidines) and acyl chlorides (2,3-dimethoxybenzoyl chloride and 3-acetoxy-2-methylbenzoyl chloride) in a slightly basic medium (Cakmak et al., 2016;Demir et al., 2015).

Structural commentary
The molecular structure of the title compound is shown in Fig. 1. The bond distances and angles are found to be in good agreement with those in analogous structures (Demir et al., 2015;Tahir et al., 2011). In the molecule, the benzene rings are nearly coplanar, with a dihedral angle of 4.89 (8) . An intramolecular N-HÁ Á ÁO hydrogen bond (Table 1) occurs between the imino and methoxy groups.

Supramolecular features
In the crystal, adjacent molecules are linked by weak C-HÁ Á ÁO hydrogen bonds, forming supramolecular chains propagating along the a-axis direction (Table 1, Fig. 2).stacking is observed between parallel benzene rings of adjacent chains, the centroid-to-centroid distance being 3.6491 (10) Å .

Hirshfeld surface analysis
Three-dimensional Hirshfeld surfaces (HS) were generated using Crystal Explorer 3.1 (Wolff et al., 2013) based on the results of the single crystal X-ray diffraction studies. Twodimensional fingerprint plots (FPs) provide a visual representation of crystal-packing interactions in the structure. The HS is a useful tool for describing the surface characteristics and gaining additional insight into the intermolecular interactions of the molecules.
The molecular Hirshfeld surface, d norm , is depicted in Fig. 3 and mapped over the range À0.1763 to 1.2643 Å . Strong hydrogen-bond interactions, such as C-HÁ Á ÁO, are seen as a bright-red area on the Hirshfeld surfaces (Ş en et al., 2017). The fingerprint plots over the Hirshfeld surfaces illustrate the significant differences between the intermolecular interaction patterns. In Fig. 4, it is observed N inside Á Á ÁH outside = 2.3%, C inside Á Á ÁH outside = 15.7%, O inside Á Á ÁH outside = 29.7%, H inside Á Á ÁH outside = 38% and all atoms inside Á Á Áall atoms outside = 100% of the total interactions. Fig. 4 shows that the major contributions are from HÁ Á ÁH (38%) and OÁ Á ÁH (30%) interactions. Fig. 5 illustrates the distribution of positive and negative potential over the Hirshfeld surfaces. Blue regions correspond to positive electrostatic potential (indicating hydrogen-bond donors) and the red regions to negative electrostatic potential (indicating hydrogen-bond acceptors) (Kumar et al., 2013).

Figure 2
Packing of the title compound in the unit cell. Dashed lines indicate the C-HÁ Á ÁO hydrogen bonds (see Table 1).

Figure 1
The molecular structure of the title compound, with displacement ellipsoids drawn at the 50% probability level. The intramolecular N-HċO (Table 1)

Synthesis and crystallization
To a solution of 4-nitroaniline (10 mmol) and triethylamine (10 mmol) in THF (10 ml) was added dropwise a THF (10 ml) solution of 2,3-dimethoxybenzoyl chloride (11 mmol) at room temperature. The reaction mixture was stirred at room temperature for 15 h and then the resulting white salt precipitate was filtered off and then 150 ml water was added dropwise to the filtrate. The precipitate was filtered off and washed several times with water to remove excessive aniline Hirshfeld surface fingerprint of the title compound, (a) N inside Á Á ÁH outside (2.3%), (b) C inside Á Á ÁH outside (15.7%), (c) O inside Á Á ÁH outside (29.7%), (d) H inside Á Á ÁH outside (38%), (e) all atoms inside Á Á Áall atoms outside (100% of total interactions).

Figure 5
Electrostatic potential mapped on the Hirshfeld surface with AE0.25 au Figure 6 The FT-IR spectrum of the title compound.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The imino-H atom was located in a difference-Fourier map. All C-bound H atoms were positioned geometrically and refined using a riding model with C-H = 0.93-0.97 Å and U iso (H) = 1.2-1.5U eq (C).    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.