1-Dibromomethyl-4-methoxy-2-nitrobenzene

The asymmetric unit of the title compound, C8H7Br2NO3, comprises two crystallographically independent molecules (A and B). The nitro groups are twisted from the attached benzene rings, making dihedral angles of 39.26 (9) and 35.90 (9)° in molecules A and B, respectively. In each molecule, the dibromomethyl group is orientated in such a way that the two Br atoms are tilted away from the benzene ring. An interesting features of the crystal structure is the two short Br⋯Br interactions which, together with intermolecular C—H⋯O hydrogen bonds, link the molecules into an extended three-dimensional network. The crystal structure is further stabilized by weak C—H⋯π interactions.

The asymmetric unit of the title compound, C 8 H 7 Br 2 NO 3 , comprises two crystallographically independent molecules (A and B). The nitro groups are twisted from the attached benzene rings, making dihedral angles of 39.26 (9) and 35.90 (9) in molecules A and B, respectively. In each molecule, the dibromomethyl group is orientated in such a way that the two Br atoms are tilted away from the benzene ring. An interesting features of the crystal structure is the two short BrÁ Á ÁBr interactions which, together with intermolecular C-HÁ Á ÁO hydrogen bonds, link the molecules into an extended three-dimensional network. The crystal structure is further stabilized by weak C-HÁ Á Á interactions.

S1. Comment
Brominated organic compounds are important synthetic intermediates and products in organic chemistry (Augustine et al., 2007). They are found in C-C coupling reactions, as precursors to organometallic species and in nucleophilic substitutions (Tyeklar et al., 1993). They are also used for the synthesis of useful pharmaceutical materials and agrochemicals (Derdau et al., 2003). However the use of molecular bromine as an electrophilic brominating reagent has several drawbacks arising from its toxic and corrosive nature and its high reactivity (Tyeklar et al., 1993). Alternative brominating reagents such as N-bromosuccinimide make for easier handling and result in improved selectivity (Khatuya, 2001).
In the asymmetric unit of the title compound, there are two crystallographically independent molecules, designated A and B (Fig. 1). In each molecule, the nitro group is twisted from the mean plane of the C1-C6 benzene ring, as shown by the dihedral angle formed between the mean plane through C5/N1/O2/O3 and the C1-C6 benzene ring of 39.26 (9)° in molecule A; the comparable angle is 35.90 (9)° for molecule B. Meanwhile, the dibromomethyl group is orientated in such a way that the two Br atoms are tilted away from the benzene ring. The bond lengths and angles are comparable to those found in related structures (Fun, Chantrapromma, Maity et al., 2009;Fun, Chantrapromma, Sujith et al., 2009;Yeap et al., 2008).

S2. Experimental
Benzoyl peroxide (0.20 g, 10 %) and N-bromosuccinimide (6.38 g, 0.0358 mol) were added in portions to a solution of 4methyl-2-nitroanisole (2.00 g, 0.0119 mol) in CCl 4 (20 ml). The reaction mixture was heated at 85 °C under a nitrogen atmosphere for 12 h. The reaction mass was cooled and filtered. The filtrate was concentrated to produce a crude product.
The latter was recrystallized with hexane to afford the title compound as a colourless crystalline solid. The yield was 3.50 g, 92 %. M.p. 370-373 K.

S3. Refinement
The H-atoms bound to C7A and C7B were located from the difference Fourier map and allowed to refine freely. The other H-atoms were placed in calculated positions, with C-H = 0.93 Å, U iso (H) = 1.2U eq (C) for aromatic, and C-H = 0.96 Å, U iso (H) = 1.5U eq (C) for methyl group; these aromatic and methyl group H atoms were refined as riding on their parent atoms. A rotating group model was used for the methyl group.  The molecular structure of the asymmetric unit of the title compound, showing 50% probability displacement ellipsoids and the atom-numbering scheme. Hydrogen atoms are shown as spheres of arbitrary radius.  Three-dimensional extended network, viewed along the a axis. Intermolecular interactions are shown as dashed lines.  (Cosier & Glazer, 1986) operating at 100.0 (1)K. 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 > 2sigma(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.