1-(6,8-Dibromo-2-methylquinolin-3-yl)ethanone

Two independent molecules,1 and 2, with similar conformations comprise the asymmetric unit in the title compound, C12H9Br2NO. The major difference between the molecules relates to the relative orientation of the ketone–methyl groups [the C—C—C—C torsion angles are −1.7 (6) and −16.8 (6)° for molecules 1 and 2, respectively]; in each case, the ketone O atom is directed towards the ring-bound methyl group. The crystal packing comprises layers of molecules, sustained by C—H⋯O and π–π {ring centroid(C6) of molecule 2 with NC5 of molecule 1 [3.584 (3) Å] and NC5 of molecule 2 [3.615 (3) Å]} interactions. C—H⋯Br contacts also occur.

Two independent molecules,1 and 2, with similar conformations comprise the asymmetric unit in the title compound, C 12 H 9 Br 2 NO. The major difference between the molecules relates to the relative orientation of the ketone-methyl groups [the C-C-C-C torsion angles are À1.7 (6) and À16.8 (6) for molecules 1 and 2, respectively]; in each case, the ketone O atom is directed towards the ring-bound methyl group. The crystal packing comprises layers of molecules, sustained by C-HÁ Á ÁO and -{ring centroid(C 6 ) of molecule 2 with NC 5 of molecule 1 [3.584 (3) Å ] and NC 5 of molecule 2 [3.615 (3) Å ]} interactions. C-HÁ Á ÁBr contacts also occur.

Comment
Quinoline derivatives continue to attract wide interest owing to their occurrence in natural products and for their biological activity (Kalluraya & Sreenivasa, 1998;Xiang et al., 2006). In continuation of structural research in this area (Prasath et al., 2011), the title compound, (I), was investigated.
Two independent molecules comprise the crystallographic asymmetric of (I), Fig. 1. The molecules are virtually superimposable as seen in Fig. 2. The r.m.s. deviations for the bond distances and angles are 0.0088 Å and 0.507 °, respectively (Spek, 2009). The major differences between the molecules are manifested in the values of the C7-C8-C11-C12 and C19-C20-C23-C24 torsion angles of -1.7 (6) and -16.8 (6) °, respectively indicating a twist of the ketone residue out of the plane of the quinolinyl ring in the second independent molecule. In each case, the ketone-O atom is directed towards the ring-methyl group.
In the crystal packing, C-H···O, Table 1, and π-π interactions are noted. The C-H···O and two closest π-π interactions lead to the formation of layers in the ac plane. The π-π interactions occur between the (C13-C18) ring and each of the 1 -x, 1 -y, 2 -z. The resultant layers stack along the b axis, Fig. 3.

Experimental
To a mixture of 2-amino-3,5-dibromobenzaldehyde (0.01 M, 2.70 g) and acetylacetone (0.01 M, 1.02 ml), 10 ml of 1 N HCl was added. The reaction mixture was stirred at 363 K for 3 h. At the end of this period, the resulting suspension was neutralized with 10 ml of 1 N NaOH. The resultant solid was filtered, dried and purified by column chromatography using a 1:1 mixture of chloroform and hexane. Recrystallization was by slow evaporation of a chloroform solution of (I) which yielded light-brown prisms. Yield: 90%. M.pt. 433-435 K.

Refinement
Carbon-bound H-atoms were placed in calculated positions [C-H 0.95 to 0.98 Å, U iso (H) = 1.2 to 1.5U eq (C)] and were included in the refinement in the riding model approximation. The maximum and minimum residual electron density peaks of 1.60 and 1.38 e Å -3 , respectively, were located 0.93 Å and 0.70 Å from the Br3 and Br2 atoms, respectively.
supplementary materials sup-2 Figures Fig. 1. The molecular structures of the two independent molecules comprising the asymmetric unit of (I) showing displacement ellipsoids at the 70% probability level. Fig. 2. Overlay diagram of the two independent molecules comprising the asymmetric unit of (I). The first independent molecule (with atom S1) is shown in red.