(E)-3-(3-Bromophenyl)-1-(4-methylphenyl)prop-2-en-1-one

The title compound, C16H13BrO, was synthesized from the reaction of 3-bromobenzaldehyde and 4-methylacetophenone in the presence of KOH. The molecule adopts an E configuration with respect to the C=C double bond of the propenone unit. The dihedral angle formed by the aromatic rings is 46.91 (14)°. The crystal structure is stabilized by Br⋯Br interactions [3.4549 (11) Å].


S1. Comment
Chalcones are a class of naturally occurring compounds with interesting biological properties such as cytotoxicity (Pandey et al., 2005), antiherpes activity and antitumour activity (Conti, 2006) and may be useful for the chemotherapy of leishmaniasis among others (Lawrence et al., 2001). Chalcone derivatives are also used as antibiotics (Nielsen et al., 2005) and as anti malerials (Dominguez et al., 2005). Recently, the crystal structures of some methyl-and bromosubstituted chalcones have been reported by our group (Sarojini et al., 2007 and references cited therein). In a continuation of our studies, the title chalcone derivative was synthesized and its crystal structure is reported here.
The molecule of the title compound ( Fig. 1) adopts an E configuration with respect to the C═C double bond of the propenone unit. The two aromatic rings are not coplanar, they dihedral angle they form being 46.91 (14) °. Molecular dimensions are unexceptional. The crystal structure is stabilized by Br···Br interactions occurring between centrosymmetrically-related molecules [Br1···Br1 i = 3.4549 (11) Å; symmetry code: (i) -x, 2-y, -z].

S2. Experimental
The title compound was prepared by adding 50% KOH (2.5 ml) to a solution of 4-methylacetophenone (1.34 g, 0.01 mol) and 3-bromobenzaldehyde (1.86 g, 0.01 mol) in ethanol (25 ml) at 273 K. The mixture was stirred for an hour and poured into crushed ice. The resulting yellow precipitate was collected by filtration and purified by recrystallization from ethanol. Single crystals suitable for X-ray analysis were grown by slow evaporation of an acetone solution (yield 80%).

S3. Refinement
All H atoms were placed at calculated positions and refined using the riding model approximation, with C-H = 0.93-0.96 Å and with U iso (H) = 1.2 U eq (C) or 1.5 U eq (C) for methyl H atoms. supporting information sup-2 Acta Cryst. (2008). E64, o2238

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