N-(4-Bromophenyl)acetamide: a new polymorph

A new polymorph of the title compound, C8H8BrNO, has been determined at 173 K in the space group P21/c. The previous room-temperature structure was reported to crystallize in the orthorhombic space group Pna21 [Andreetti et al. (1968 ▶). Acta Cryst. B24, 1195–1198]. In the crystal, molecules are linked by N—H⋯O hydrogen bonds forming chains along [010]. Weak C—H⋯π interactions are also present.

BN thanks the UGC, New Delhi, and the Government of India for the purchase of chemicals through the SAP-DRS-Phase-1 programme and a BSR one-time grant. JPJ acknowledges the NSF-MRI program (grant No. CHE1039027) for funds to purchase the X-ray diffractometer.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: SU2566).

sup-1
Acta Cryst.  (Mijin et al., 2006(Mijin et al., , 2008. Amides are also used as ligands due to their excellent coordination abilities (Wu et al., 2008(Wu et al., , 2010. The room temperature crystal structure of the title compound was reported without hydrogen atom coordinates in the orthorhombic space group Pna2 1 (Andreetti et al., 1968). We report herein on the crystal structure of the monoclinic polymorph that crystallized in space group P2 1 /c.
Experimental 4-Bromo aniline (0.172 g, 1 mmol) was dissolved in acetic acid (20 ml) and refluxed for 4 h. The solution was then cooled and poured into 100 ml of ice-cold water with stirring. The precipitate obtained was filtered, washed with water and dried. Block-like yellow crystals were grown from a solution in ethyl acetate by slow evaporation of the solvent (M.p.: 430 K).

Refinement
The NH H atom was located in a difference Fourier map and refined as a riding atom: N-H = 0.89 Å with U iso (H) = 1.2U eq (N). The C-bound H atoms were placed in calculated positions and refined as riding atoms: C-H = 0.95 Å (CH) and 0.98 Å (CH 3 ) with U iso (H) = 1.2U eq (C) for CH H atoms and = 1.5U eq (C) for CH 3 H atoms.

Computing details
Data collection: CrysAlis PRO (Oxford Diffraction, 2010); cell refinement: CrysAlis PRO (Oxford Diffraction, 2010); data reduction: CrysAlis RED (Oxford Diffraction, 2010); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).    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.