N,N′-(1,4-Phenylene)bis(2-bromo-2-methylpropanamide)

The molecular structure of the title compound, C14H18Br2N2O2, has one half-molecule in the asymmetric unit. The molecule has a crystallographic inversion centre in the middle of the benzene ring. The C—C—N—C torsion angle between the benzene ring and the bromoamide group is 149.2 (7)°. The crystal is stabilized by a strong intermolecular N—H⋯O bond and weak C—H⋯O interactions. These contacts give rise to a three-dimensional network.


Experimental
p-Phenylenediamine is a precursor to aramid plastics and fibers such as Kevlar (Rollison et al., 2006). p-Phenylenediamine is also used as a developing agent in the color photographic film development process, reacting with the silver grains in the film and creating the colored dyes that form the image. p-Phenylenediamine derivatives such as chloroquine are the most important and widely used class of drugs for treatment of malaria (Miroshnikova et al., 2007). In the title compound C 14 H 18 Br 2 N 2 O 2 , the torsion angle between the phenyl ring and the bromo amide group is 149.2 (7)° (C3-C1 -N1-C4). The molecule has a crystallographic inversion centre in the middle of the phenyl ring. The crystal is stabilized by a strong intermolecular N-H···O bonding and weak C-H···O interactions. These contacts gives rise to a three dimensional network.
Experimental p-Phenylene diamine (5 g, 0.012 moles), triethylamine (12 g, 0.05 moles) and THF (400 ml) were placed in a 3-neck round bottomed flask. Bromoisobutyrl bromide (13.7 g, 0.05 moles) was added slowly, using a syringe, with stirring, upon which a brown precipitate of triethylammonium bromide was formed. The mixture was left to react for 12 h, with stirring. Subsequently, triethylammonium bromide, the precipitate was removed by filtration and the THF was removed by rotary evaporation. The resulting crude product was dissolved in ethyl acetate, washed with bicarbonate solution and then with water thrice followed by brine solution and dried over anhydrous sodium sulfate. The resulting solvent was removed by rotary evaporation. The product was purified by column chromatography technique using 10% ethyl acetate in hexane as the eluent to obtain pure initiator as a bright yellow solid. Recrystallization of the compound from hexane gave X-ray diffraction quality crystals of N,N′-(1,4-phenylene)bis(2-bromo-2-methylpropanamide).

Refinement
All hydrogen atoms were fixed geometrically and allowed to ride on the parent carbon atoms, with aromatic C-H = 0.93 Å, methyl C-H = 0.96 Å and methylene C-H = 0.97 Å. The displacement parameters were set for phenyl and methylene H atoms at U iso (H) = 1.2U eq (C) and methyl H atoms at U iso (H) = 1.5U eq (C).
The crystal data was collected up to 0.73 Å resolution, the crystal (the largest available) still diffracted quite weakly at high angle. On repeated crystallization we could get only small crystals which weakly diffracted. The data completeness we could get was only 93.6%.

Figure 1
ORTEP of the molecule with atoms represented as 30% probability ellipsoids. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.54 e Å −3 Δρ min = −0.56 e Å −3 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 > 2sigma(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.