1,5-Dibromo-2,4-dimethoxybenzene

In the title compound, C8H8Br2O2, all non-H atoms lie essentially in a common plane (r.m.s deviation of all fitted non-H atoms = 0.0330 Å). In the crystal, weak C—H⋯O hydrogen bonds connect the molecules, forming chains which extend along the b-axis direction.

In the title compound, C 8 H 8 Br 2 O 2 , all non-H atoms lie essentially in a common plane (r.m.s deviation of all fitted non-H atoms = 0.0330 Å ). In the crystal, weak C-HÁ Á ÁO hydrogen bonds connect the molecules, forming chains which extend along the b-axis direction.

Related literature
For background to the pharmacological importance of the title compound, see: Pahari & Rohr (2009). For the synthesis of the title compound, see: Yang et al. (2009). For a report listing the crystal structure of 1-bromo-5-chloro-2,4-dimethoxybenzene but entered incorrectly as the title compound in the CSD (TASBAR), see: Yang et al. (2005). For graph-set analysis of hydrogen bonds, see: Bernstein et al. (1995).  Table 1 Hydrogen-bond geometry (Å , ).
Data collection: APEX2 (Bruker, 2010); cell refinement: SAINT (Bruker, 2010); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 2012) and Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXL97 and PLATON (Spek, 2009 (Pahari et al., 2009). The crystal structure of 1-bromo-5-chloro-2,4dimethoxybenzene has been determined (Yang et al., 2005), but the compound was in fact reported erroneously as 1,5-dibromo-2,4-dimethoxybenzene in the CSD (CCDC 271922, ref-code: TASBAR). The error is the result of 50% rotational disorder between the two halogen atoms in the molecule and this fact is also mentioned among the deposited experimental details in the CSD entry. Furthermore, the cell constants reported in this entry [a = 7.722 (4) of the title compound. In view of the importance of the title compound in synthetic as well as medicinal chemistry, and to rectify the anomaly in the deposited crystallographic data, it was resynthesized and the crystal structure is reported herein.
The title compound is essentially planar (r.m.s. of all fitted non-hydrogen atoms = 0.0330 Å), with one of the methyl carbon atoms deviating most from this common plane by -0.073 (2) Å (Fig. 1). Intracyclic C-C-C angles cover a range from 118.96 (16) ° to 120.73 (17)° with the smallest angle found at one of the carbon atoms bearing a methoxy substituent (C4) and the largest angle at the bromo-substituted carbon atom (C1) in the para position to C4.
In the crystal, a weak intermolecular methyl C-H···O contact (Table 1) whose value falls slightly below the sum of van-der-Waals radii of the atoms participating, is observed, connecting the molecules into chains which extend along b (Fig. 2). A C1-Br1···Cg ii contact is also present. According to a graph-set analysis (Bernstein et al., 1995), the descriptor for the C-H···O contacts is C(7). The shortest intercentroid distance between two aromatic ring systems is 4.0267 (10) Å ( Fig. 3).

Refinement
Carbon-bound H atoms were placed in calculated positions [C-H(aromatic) = 0.95 Å and C-H(methyl) = 0.98 Å] and with U iso (H) = 1.2U eq (C) (aromatic) and allowed to ride in the refinement. The H atoms of the methyl groups were allowed to rotate with a fixed angle around the C-C bond to best fit the experimental electron density, with U iso (H) = 1.5U eq (C).