2-(4-Isobutylphenyl)-N′-[1-(4-nitrophenyl)ethylidene]propanohydrazide

The molecule of the title compound, C21H25N3O3, exists in a trans configuration with respect to the ethylidene unit. The dihedral angle between the two substituted benzene rings is 86.99 (7)°. The nitro group is twisted from the attached benzene ring at an angle of 17.02 (7)°. In the crystal structure, molecules are linked by pairs of N—H⋯O hydrogen bonds in a face-to-face manner into centrosymmetric dimers. These dimer units are further linked into chains along the c axis by weak C—H⋯O interactions. These chains are stacked along the b axis. The crystal is further stabilized by weak C—H⋯π interactions.

The molecule of the title compound, C 21 H 25 N 3 O 3 , exists in a trans configuration with respect to the ethylidene unit. The dihedral angle between the two substituted benzene rings is 86.99 (7) . The nitro group is twisted from the attached benzene ring at an angle of 17.02 (7) . In the crystal structure, molecules are linked by pairs of N-HÁ Á ÁO hydrogen bonds in a face-to-face manner into centrosymmetric dimers. These dimer units are further linked into chains along the c axis by weak C-HÁ Á ÁO interactions. These chains are stacked along the b axis. The crystal is further stabilized by weak C-HÁ Á Á interactions.

Related literature
For reference structural data, see: Allen et al. (1987). For related structures, see, for example: Fun et al. (2008). For background to the activities and applications of hydrazones, see, for example: Amir & Kumar (2007) Table 1 Hydrogen-bond geometry (Å , ).

Comment
Hydrazones have been prepared by treating aryl hydrazines with carbonyl compounds using a variety of solvents in presence or absence of an acidic catalyst. (Pasha & Nanjundaswamy, 2004). Aryl hydrazones are important building blocks for the synthesis of a variety of heterocyclic compounds such as pyrazolines and pyrazoles (Sridhar & Perumal, 2003). Hydrazones have been demonstrated to possess variety of pharmacological activities (Bedia et al., 2006;Rollas et al., 2002;Terzioglu & Gürsoy, 2003). These observations have been the guidelines for the development of new hydrazones that possess varied biological activities. Similarly ibuprofen is also known for their pharmaceutical activities and belongs to the class of nonsteroidal anti-inflammatory drugs (Amir & Kumar, 2007). According to our previous work, we are interested in the synthesis and crystal structure of ibuprofen containing hydrazone derivatives (Fun et al., 2008). Prompted by the biological activities of hydrazones and ibuprofen, the title compound was synthesized and it crystal structure was reported here.
In the structure of the title compound, (I), the molecule exist in a trans configuration with respect to the ethylidene C9═N2 unit (Fig. 1). The dihedral angle between the two substituted benzene rings is 86.99 (7)°. In the 4-nitrophenyl unit, the nitro group is twisted from the mean plane of the C10-C15 ring which can be shown by the dihedral angle between the mean planes through the C13/N3/O2/O3 group and the C10-C15 ring being 17.02 (7)°. Atoms O1, N1, N2, C7, C8, C9 and C21 lie on the same plane with a maximum deviation of -0.032 (1)Å for atom N1. This plane makes dihedral angles of 73.01 (6) and 15.02 (5)° with the C1-C6 and C10-C15 benzene rings, respectively. The isobutyl substituent (C16-C19) is (-)-synclinal with respect to the C1-C6 ring with the torsion angle C2-C3-C16-C17 being -76.91 (14)°. The bond distances have normal values (Allen et al., 1987) and are comparable with the related structure (Fun et al., 2008).
In the crystal packing, N-H···O hydrogen bonds (Table 1 and Fig. 2) link the molecules into face-to-face dimers. These dimers are further linked into chains along the c axis and these chains are stacked along the b axis. The crystal is stabilized by N-H···O hydrogen bonding, and weak C-H···O and C-H···π interactions (Table 1); Cg1 and Cg2 are the centroids of the C1-C6 and C10-C15 rings, respectively (Table 1).

Experimental
The title compound was obtained by refluxing 2-[4-(2-methylpropyl)phenyl]propanehydrazide (0.01 mol) and 4-nitroacetophenone (0.01 mol) in ethanol (30 ml) by adding 3 drops of concentrated Sulfuric acid for 1 h. Excess ethanol was removed from the reaction mixture under reduced pressure. The solid product obtained was filtered, washed with ethanol and dried. Colorless single crystals suitable for X-ray analysis were obtained from ethanol by slow evaporation (yield 74%; m.p. 443 K).