2-(4-Methylphenyl)-6-nitro-1,3-benzoxazole

The title compound, C14H10N2O3, is a π-conjugated molecule containing a benzoxazole aromatic fused heterobicycle. The benzoxazole ring system is planar within 0.01 Å. The molecule assumes an approximately flat conformation, the benzoxazole ring system forming dihedral angles of 6.52 (12) and 7.4 (3)° with the benzene ring and the nitro group, respectively. In the crystal, molecules are connected by very weak C—H⋯O hydrogen interactions, forming chains running parallel to the a or c axes. The methyl H atoms are disordered over two sets of sites of equal occupancy rotated by 60°.

The title compound, C 14 H 10 N 2 O 3 , is a -conjugated molecule containing a benzoxazole aromatic fused heterobicycle. The benzoxazole ring system is planar within 0.01 Å . The molecule assumes an approximately flat conformation, the benzoxazole ring system forming dihedral angles of 6.52 (12) and 7.4 (3) with the benzene ring and the nitro group, respectively. In the crystal, molecules are connected by very weak C-HÁ Á ÁO hydrogen interactions, forming chains running parallel to the a or c axes. The methyl H atoms are disordered over two sets of sites of equal occupancy rotated by 60 .
The molecular structure of the title compound is shown in Fig. 1. The phenyl and benzoxazole rings are nearly coplanar, the dihedral angle between the mean planes being 6.7 (1)°. That structural feature is in accordance with the expected π conjugation of the compound.
Molecules in the crystal form rows through very weak hydrogen interactions between methyl or aromatic C-H donors and oxygen acceptors of the nitro group ( Fig. 2 and Fig. 3; Table 1). The chains, which have graph set symbol C 1 1 (14) and C 1 1 (7) are generated, respectively, by the b and a glide planes.

Experimental
The title compound was prepared by reaction of 2-amino-5-nitrophenol (5.00 g, 32.4 mmol) with toluic acid (4.41 g, 32.4 mmol) in polyphosphoric acid (150 g) at 150°C. The dehydration procedure is analogous to that we have already described for the synthesis of similar chromophores (Bruno et al., 2002;Centore et al., 2007). Purification of the title compound was obtained by recrystallization from ethanol. The final yield was 5.69 g (69%

Refinement
All H atoms were generated stereochemically. In particular, the methyl group is disordered over two sets of sites of equal occupancy rotated from each other by 60°. All H atoms were refined by a riding model with C-H = 0.93-0.96 Å and with U iso (H) = 1.2U eq (C) or 1.5U eq (C) for methyl hydrogen atoms.

Figure 1
ORTEP view of the molecular structure of the title compound. Thermal ellipsoids are drawn at 50% probability level.
Only one orientation of the disordered methyl group is shown. Row of molecules of the title compound running along the c. Only one orientation of the disordered methyl group is shown. Hydrogen bonds are shown as dashed lines. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.14 e Å −3 Δρ min = −0.19 e Å −3

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. 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.

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