2-(4-Bromophenyl)-2-methylpropanamide

In the crystal of the title compound, C10H12BrNO, inversion dimers linked by pairs of N—H⋯O hydrogen bonds generate R 2 2(8) loops. Further N—H⋯O hydrogen bonds link the dimers into sheets propagating in (100).


Comment
The reaction of amides towards weak nucleophiles such as nonactivated arenes have very broad utility in organic chemistry.
However, little work has been done to investigate it. The title compound was synthesized by a facile method through the reaction of methacrylamide and benzene, catalyzed by AlCl 3 . In the crystal, the molecules are linked by intermolecular N-H···O hydrogen bonding interactions. Single-crystal X-ray diffraction analysis reveals that the title compound crystallizes in the Monoclinic space group P 21/c.

Experimental
A mixture of AlCl 3 (0.95 g, 7.1 mmol) and methacrylamide (0.2 g, 2.3 mmol) in benzene (3 ml) was stirred at 25 °C for 3 h, and was then poured over several grams of ice and extracted with CH 2 Cl 2 . The organic phase was separated, dried with anhydrous Na 2 SO 4 and concentrated in vacuo to give a solid mixture of 2-methyl-3-phenylpropionamide and 2-methyl-2phenylpropionamide (0.41 g, 97%) in 2:1 ratio. The title compound was separated by flash column chromatography on silica gel. Colourless prisms of (I) were obtained by recrystallisation from ethanol.

Refinement
The H atoms were positioned geometrically (C-H=0.95Å or 0.98 Å, N-H=0.88 Å) and refined as riding with U iso (H) = 1.2U eq (C,N) or 1.5U eq (methyl C). Fig. 1. The molecular structure of (I). Displacement ellipsoids are drawn at the 30% probability level and H atoms are shown as spheres of arbitrary radius.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 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.