2,6-Dichlorobenzaldehyde oxime

In the title compound, C7H5Cl2NO, there are two molecules in the asymmetric unit. The molecules are essentially identical. Each molecule is connected to a symmetry-related molecule through an inversion center by O—H⋯N hydrogen bonds, building an R 2 2(6) graph-set motif.

In the title compound, C 7 H 5 Cl 2 NO, there are two molecules in the asymmetric unit. The molecules are essentially identical. Each molecule is connected to a symmetry-related molecule through an inversion center by O-HÁ Á ÁN hydrogen bonds, building an R 2 2 (6) graph-set motif.

Experimental
Crystal data
In the title compound, C 7 H 6 Cl 2 NO, there are two molecules in the asymmetric unit. Both molecules are roughly identical, the oxime fragment is twisted with respect to the dichlorobenzene ring by 53.83 (11)° and 42.99 (14)° respectively ( Fig. 1).
Each molecule is connected to its symmetry related one through inversion center by O-H···N hydrogen bonds building a R 2 2 (6) graph-set motif (Etter et al., 1990;Bernstein et al., 1995) (Fig. 2 and Table 1).

S2. Experimental
2,6-dichlorobenzaldehyde (1 mmol) was dissolved in anhydrous methanol, hydroxylamine hydrochloride and sodium carbonate were added to this, the mixture was stirred for 3 h at room temperature. The product was isolated and recrystallized in dichloromethane, colourless single crystals of (I) was obtained after 5 d.

S3. Refinement
All H atoms were placed in calculated position and treated as riding on their parent atoms with C-H=0.93Å or O-H=0.82 Å with U iso (H)=1.2U eq (C) or 1.5U eq (O) for the hydroxyl H atom.  The asymmetric unit of (I) with the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level. H atoms are represented as small spheres of arbitrary radii.   where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.40 e Å −3 Δρ min = −0.31 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 > 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.