N,N-Dicyclohexyl-3,5-dinitrobenzamide

In the title compound, C19H25N3O5, the benzene ring is not coplanar with the amide group [dihedral angle = 61.90 (5)°]. The cyclohexyl rings are in chair conformations. There is a strong intermolecular interaction between the C=O group of the amide group and the nitro group of an adjoining molecule, with a short O⋯N distance of 2.7862 (17) Å. In the crystal, C—H⋯O interactions occur along the [100] direction.

In the title compound, C 19 H 25 N 3 O 5 , the benzene ring is not coplanar with the amide group [dihedral angle = 61.90 (5) ]. The cyclohexyl rings are in chair conformations. There is a strong intermolecular interaction between the C O group of the amide group and the nitro group of an adjoining molecule, with a short OÁ Á ÁN distance of 2.7862 (17) Å . In the crystal, C-HÁ Á ÁO interactions occur along the [100] direction.

Related literature
For background to the biological activity of N-substituted benzamides and their use in synthesis, see: Priya et al. (2005). For related structures and their use in molecular recognition, see: Toda et al. (1987); Saeed et al. (2011Saeed et al. ( , 2012. For puckering parameters, see Cremer & Pople (1975). For a description of the Cambridge Structural Database, see: Allen (2002 Table 1 Hydrogen-bond geometry (Å , ).
RJB acknowledges the NSF MRI program (grant No. CHE-0619278) for funds to purchase an X-ray diffractometer.

Comment
The structure of the title compound, (I), was been determined to explore the effect of substituents on the structure of benzanilides (Saeed et al., 2011(Saeed et al., , 2012. A compound with the same basic skeleton as the title compound has been used in host-guest chemistry to form numerous highly crystalline adducts with a variety of common organic solvents (Toda et al., 1987).
The crystal structure and atom numbering of (I) is shown in Fig. 1. The nitro groups are almost coplanar with the attached benzene ring (dihedral angles between phenyl ring and nitro groups being 1.74 (27) and 6.43 (33)°, respectively). As in the related structure reported recently (Saeed, et al., 2012), the phenyl ring is not coplanar with the amide moiety (dihedral angle between planes C5-C7-N3-O5 and the phenyl ring of 61.90 (5) °). Also analogous with this structure the phenyl ring is twisted out of this plane as indicated by the C4 C5 C7 O5 torsion angle of 112.76 (16) ° (in the previous structure containing two molecules in the symmetric unit these angles were 121.46 (33)° and -119.62 (34)°). The cyclohexyl rings are both in a chair conformation [the puckering parameters (Cremer & Pople, 1975) are Q(2) and φ(2) 0.018 (1) Å and 4.184 (1) ° in C8-C13, 0.025 (1) Å and 305.147 (1) ° in C14-C19). There is a strong intermolecular interaction between the C=O group of the amide moiety and the nitro group of an adjoining molecule (O5···N2 distance of 2.7862 (17) Å) so that these molecules form a dimeric unit. A search of the Cambridge Structural Database (Allen, 2002) for similar intermolecular interactions between carbonyl groups and nitro groups showed that such interactions are not universal. There were over 7000 hits for structures containing both these groups but only 515 contained such interactions with a mean distance of 2.963 Å) and a minimum of 2.73 Å. Thus this interaction in this compound is one of the strongest to be observed. While there are no classic hydrogen bonds found in the crystal, there are weak C-H···O intra-and intermolecular interactions.

Experimental
To a 250 ml round flask fitted with a condenser was added dicyclohexyl amine (0.01 mol), dichloromethane (15 ml) and triethylamine(0.5 ml) with magnetic stirring. 3,5-dinitrobenzoyl chloride (0.01 mol) was added gradually. The reaction mixture was stirred at room temperature for 1 h and then refluxed for 2 h. The product precipitated as a colorless powder, which was washed three times with water and dichloromethane. Recrystallization from ethyl acetate produced the crystals of the title compound.

Refinement
The H atoms were placed in their calculated positions with C-H 0.95 and 0.99 Å and refined using the riding model with isotropic displacement parameters set to 1.2 times U eq of the parent atoms.  An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 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.