(2E)-N-(3,5-Dibromo-4-methoxyphenyl)-2-(hydroxyimino)acetamide

The title compound, C9H8Br2N2O3, is planar (r.m.s. deviation = 0.030 Å) with the exception of the terminal methyl group which lies out of the plane [1.219 (3) Å]. The conformation about the C=N double bond [1.268 (3) Å] is E. An intramolecular N—H⋯N hydrogen bond occurs. Linear supramolecular chains along the b axis mediated by O—H⋯O hydrogen-bonding interactions feature in the crystal structure. These chains are also stabilized by weak C—H⋯N contacts.

The use of the EPSRC X-ray crystallographic service at the University of Southampton, England, and the valuable assistance of the staff there is gratefully acknowledged. SJG thanks CNPq and FAPERJ for financial support.
The molecular structure of (I), Fig. 1, is essentially planar with the exception of the terminal methyl group. Thus, the r.m.s. deviation of all non-hydrogen atoms, excluding the methyl-C9 atom, is 0.030 Å; the C9 atom lies 1.219 (3) Å out of the plane. The conformation about the C2═N2 double bond [1.268 (3) Å] is E. The observed planarity is partially stabilised by an intramolecular N-H···N hydrogen bond (Table 1). There two other methoxy substituted 2-(hydroxyimino)-N-arylacetamide structures available for comparison,i.e. o-OMe (Plana et al., 1976) and p-OMe (Briansó et al., 1974) derivatives. The geometric parameters in these match closely those in (I). The major difference in the three structures relate to the non-planarity of (I) compared to the planarity in the literature structures. The proximity of the OMe group to two bromido substituents in (I) is the likely explanation for the deviation from planarity in (I). The crystal packing is dominated by O-H···O hydrogen bonding interactions that lead to the formation of a supramolecular linear chain along the b axis, Fig. 2 and Table 1. These chains are also stabilised by weak C-H···N contacts, Table 1.

Refinement
The O-, N-and C-bound H atoms were geometrically placed (O-H = 0.84 Å, N-H = 0.88 Å and C-H = 0.95-0.98 Å) and refined as riding with U iso (H) = 1.2-1.5U eq (parent atom). Fig. 1. The molecular structure of (I) showing the atom-labelling scheme and displacement ellipsoids at the 50% probability level.

Figures
supplementary materials sup-2 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 > 2σ(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq