2,4,6-Trinitrophenyl 3-chlorobenzoate

In the title benzoate derivative, C13H6ClN3O8, the planes of the benzene rings form a dihedral angle of 73.59 (7)°. The central ester unit forms an angle of 20.38 (12)° with the chloro-substituted benzene ring. In the crystal, molecules are linked by weak C—H⋯O interactions, forming helical chains along [101] and [100].

In the title benzoate derivative, C 13 H 6 ClN 3 O 8 , the planes of the benzene rings form a dihedral angle of 73.59 (7) . The central ester unit forms an angle of 20.38 (12) with the chlorosubstituted benzene ring. In the crystal, molecules are linked by weak C-HÁ Á ÁO interactions, forming helical chains along [101] and [100].
Also, the structural information can be linked or be useful to explain the results found at investigations of reaction kinetics (Kirkien-Konasiewicz & Maccoll, 1964;Belousova et al., 2000), spectroscopic behavior and theoretical studies (Ibrahim et al., 2011) underwent over this same group of compounds. The molecular structure of (I) is shown in Fig (Allen, 2002, Version 5.33). The benzene rings of (I) form a dihedral angle of 73.59 (7)°. The central ester moiety forms an angle of 20.38 (12)° with the chloro-substituted benzene ring to which it is attached and an angle of 86.03 (7)° with the picryl ring. The nitro groups form dihedral angles with the adjacent benzene ring of 59.14 (9)°, 3.6 (2)° and 21.48 (14)° for O1-N1-O2, O3-N2-O4 and O5-N3-O6, respectively. The molecules are packed in a three dimensional network, through weak interactions C-H···O (see Table 1; Nardelli, 1995). Weak C3-H3···O3 and C11-H11···O1 contacts which reinforced each other, allow the molecules to propagate, forming one-dimensional helical chains, along [101]. Both weak contacts form dimers within the structure, as is shown in Fig. 2, and allow the formation of R 2 2 (10) and R 2 2 (22) rings respectively (Etter, 1990). In addition to the mentioned interactions other weak C-H···O interactions are observed.

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 obtained through a two-step reaction. First the 3-chlorobenzoic acid (0.20g, 0.554 mmol) was refluxed in an excess of thionyl chloride (10 ml) during an hour. Then thionyl chloride was distilled off under reduced pressure to purify the 3-chorobenzoyl chloride obtained as a pale yellow traslucent liquid. The same reaction flask was rearranged and a solution of picric acid (0.12 g, 0.554 mmol) in acetonitrile was added dropwise with constant stirring. The reaction mixture was left 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 Yellow crystals; yield 65%; m.p 408 (1)

Refinement
All the hydrogen atoms attached to C atoms were positioned at geometrically idealized positions and treated as riding with C-H= 0.93 Å with U iso (H) = 1.2 U eq (C).

Figure 1
Molecular conformation 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.

Figure 2
Part of the crystal structure of (I), forming one-dimensional helical chains, along [101]. Symmetry code: (i) -x+2,-y,-z+2; (ii) -x+1,-y,-z+1.  (iii) -x+2,+y-1/2,-z+3/2; (iv) -x+1,+y+1/2,-z+3/2. 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.