2,4,6-Trinitrophenyl furan-2-carboxylate

In the title carboxylate derivative, C11H5N3O9, the picryl ring forms an angle of 75.79 (7)° with the ester fragment, indicating a near perpendicular disposition. The nitro substituents are variously oriented with respect to the picryl ring [dihedral angles = 3.22 (10), 16.03 (12) and 36.63 (10)°]. In the crystal, molecules form helical chains sustained by C—H⋯O interactions along [010]. The furanyl residue is disordered, having two coplanar slightly displaced orientations [major component = 0.730 (9)].


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 2-furoyl chloride (0.252 g, 1.931 mmol) and picric acid (0.442 g). 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 its acetonitrile solution. IR spectra were recorded on a FT-IR SHIMADZU IR-Affinity-1 spectrophotometer. Pale Yellow crystals; yield 52%; m.p 383 (1) K. IR (KBr) 3088.17 cm -1 (aromatic C-H); 1764.94 cm -1 (ester C=O); 1544.08 cm -1 , 1343.48 cm -1 (-NO2); 1234.50 cm -1 (C(=O)-O).

Refinement
Bond lengths of the disordered furanyl ring were restrained to 1.37 (1) Å for C-O and 1.325 (20) and 1.45 (2) Å for the formally double and single C-C bonds, respectively. Restraints were also applied to force equivalence of displacement parameters for each pair of disordered atoms. All H-atoms were positioned at geometrically idealized positions with C-H distances of 0.95 Å, and with U iso (H) = 1.2U eq of the parent C-atoms. 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).

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. In the disordered furanyl residue, the atoms labelled with an "a" have site occupancy factors of 0.730 (9).

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (