5,7-Dibromo-2-methylquinolin-8-ol

In the title compound, C10H7Br2NO, the molecule possesses a planar geometry with an r.m.s deviation of 0.0383 Å for all non-H atoms. The crystal structure displays O—H⋯N and C—H⋯O hydrogen bonding, as well as Br⋯Br contacts [3.6284 (4) Å].

In the title compound, C 10 H 7 Br 2 NO, the molecule possesses a planar geometry with an r.m.s deviation of 0.0383 Å for all non-H atoms. The crystal structure displays O-HÁ Á ÁN and C-HÁ Á ÁO hydrogen bonding, as well as BrÁ Á ÁBr contacts [3.6284 (4) Å ].
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: IM2267).

Comment
The molecular shape of the title compound is best described by the planarity of the molecule (Fig. 1), expressed by the RMS deviation of all non-hydrogen fitted atoms being 0.0383 Å. Molecular dimers are formed by a conventional hydrogen bridge, O1-H1···N1 [d = 2.707 (2) Å, θ = 157°] (Fig. 2) that is also found in the structure of the parent 8-hydroxyquinoline (Banerjee & Saha, 1986). In addition, a C-H···O contact creates chains along the crystallographic b axis. Distances between adjacent aromatic planes of 4.1 Å indicate the absence of π stacking interactions. However, halogen interactions of type I mode (Awwadi et al. 2006) represented by the Br2···Br2 contact [d = 3.6284 (4) Å, θ 1 = θ 2 = 143.3°] connect the formed dimers. Considering analogous dimer formation in the parent 8-hydroxyquinoline, this particular halogen contact is largely attributable to crystal packing effects.

Experimental
As described by Choi & Chi (2004), 5 ml of bromine in MeOH (50 ml) was added to a mixture of 8-hydroxy-2-methylquinoline (5.0 g, 31.4 mmol), NaHCO 3 (5 g) and MeOH (50 ml). After stirring for 5 min at room temperature, Na 2 SO 3 (2.5 g) was added, and then the mixture was filtered and washed with H 2 O (100 ml). The white solid was dried in vacuo to give the title compound as raw product (8.9 g, 89%). Recrystallization from boiling and slowly cooling to room temperature ethanol yielded single crystals suitable for X-ray crystallography.

Refinement
H atoms were positioned geometrically and allowed to ride on their parent atoms, with O-H = 0.84 Å, C-H = 0.95-0.98 Å and U iso (H) = 1.2-1.5 U eq (parent atom).   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 Rfactors(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.