2,4,6-Trinitro-phenyl benzoate.

In the title mol-ecule, C13H7N3O8, the phenyl and benzene rings are rotated from the mean plane of the central ester group by 18.41 (9) and 81.80 (5)°, respectively. The dihedral angle between the rings is 80.12 (14)°. In the crystal, mol-ecules are linked by weak C-H⋯O inter-actions, forming helical chains along [010].

In the title molecule, C 13 H 7 N 3 O 8 , the phenyl and benzene rings are rotated from the mean plane of the central ester group by 18.41 (9) and 81.80 (5) , respectively. The dihedral angle between the rings is 80.12 (14) . In the crystal, molecules are linked by weak C-HÁ Á ÁO interactions, forming helical chains along [010].
Data collection: CrysAlis PRO (Oxford Diffraction, 2010); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012) and Mercury (Macrae et al., 2006); software used to prepare material for publication: WinGX (Farrugia, 2012 In our research group, we have recently investigated the synthesis, crystalline properties and main structural features of nitro aryl benzoates, in particular, the derivatives of picric acid (trinitrophenol -TNP). These types of compounds have been synthetically obtained and studied at a spectroscopic and theoretical level (Ibrahim et al., 2011) but there are no prior entries in Cambridge Structural Database (Version 5.33, Allen, 2002) of such related esters. Consequently, there is an absence of structural information about these esters. In order to fulfill this absence, we present the structure determination of the title compound, as part of a group of nitro aryl benzoates such as 2,4,6-trinitrophenyl-3-methylbenzoate (TNP3MeBA) and 2,4,6-trinitrophenyl-4-methylbenzoate (TNP4MeBA), the structures of which are already published (Moreno-Fuquen et al., 2012a,b).
The molecular structure of (I) is shown in Fig. 1, with a numbering scheme similar to that for TNP3MeBA and However, if these structural parameters are strictly checked in other phenyl benzoates having no nitro substituent over the structure (Shibakami & Sekiya, 1995, Gowda et al., 2007, it should be noticed that the phenolic C1-O7 bond length is significantly shortened [1.3695 (19) Å] and the benzoic C7-O7 bond length is significantly elongated [1.3876 (17) Å].
These changes in the bond parameters in (I) seem to be a feature of this kind of nitro phenyl benzoates , as they were found also in TNP3MeBA and TNP4MeBA, and are probably related with the presence of nitro substituents in the structure. Such effects have been well described by other authors (Kirkien-Konasievicz & Maccoll, 1964;Domenicano et al., 1990;Ibrahim et al., 2011) in a large varied number of other organic structures and can be rationalized in terms of inductive, resonance, reactivity and steric effects produced by nitro groups over aromatic rings. The benzene rings of (I) form a dihedral angle of 80.12 (14) Fig. 2). The C3 atom of the phenyl ring at (x,y,z) acts as a hydrogen-bond donor to carbonyl atom O8 at (-x,+y-1/2,-z+1/2) (see Table 1; Nardelli, 1995). This molecular interaction, involving the same atoms and given akin supramolecular behavior, is also found in TNP3MeBA and TNP4MeBA. For (I), the interaction is defined by distance D..A [3.388 (2)  level among these group of compounds; very uncommon if it is taken into account that small changes in the molecular structures of a group of molecules usually lead to large changes in molecular aggregation of the structures (Glidewell et al., 2005).

Experimental
The reagents and solvents for the synthesis were obtained from the Aldrich Chemical Co., and were used without additional purification. The title molecule was synthesized using equimolar quantities of benzoyl chloride (0.235 g, 1.673 mmol) and picric acid (0.383g). The reagents were dissolved in acetonitrile and the solution was taken to reflux for about an hour. A pale yellow solid was obtained after leaving the solvent to evaporate. The solid was washed with distilled water and cold methanol to eliminate impurities. Crystals of good quality and suitable for single-crystal X-ray diffraction were grown from acetonitrile. IR spectra were recorded on a FT-IR SHIMADZU IR-Affinity-1 spectrophotometer. Pale

Refinement
All H-atoms were positioned at geometrically idealized positions with C-H distance of 0.93 Å and U iso (H) = 1.2 times U eq of the C-atoms to which they were bonded.

Figure 1
The molecular structure and atom numbering scheme for the title compound with displacement ellipsoids drawn at the 50% probability level. H atoms are shown as spheres of arbitrary radius.  Part of the crystal structure of (I), showing the formation of helical chains along [010]. Symmetry code: (i) -x,+y-1/2,-z+1/2. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.17 e Å −3 Δρ min = −0.21 e Å −3 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 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.