4-[(E)-(Hydroxyimino)methyl]-N,N-dimethylanilinium chloride

In the title compound, C9H13N2O+·Cl−, the cation, apart from the methyl groups, is almost planar, with a maximum deviation of 0.040 (1) Å; the methyl C atoms deviate by 0.389 (2) and −1.247 (1) Å, from the mean plane. In the crystal, cations and anions associate through C—H⋯Cl hydrogen bonds, forming a helical arrangement. In addition, intermolecular O—H⋯Cl, N—H⋯Cl and C—H⋯N interactions are observed.

Experimental Crystal data
The X-ray study confirmed the molecular structure of the title compound as illustrated in Fig. 1. Atom H1N was located from a difference Fourier map and refined freely. The protonation on the N1 site of the cation is also confirmed from the C1-N1 bond distance of 1.4777 (14) Å in comparison with the C-N bond distance of 1.380 (4) Å observed in the crystal structure of the neutral α-p-dimethylaminobenzaldoxime (Bachechi & Zambonelli, 1972). The bond distance N2 -C7 of 1.267 (2) Å confirms the double bond character. The cation is almost planar with a maximum deviation of -0.040 (1) Å for atom C3 and the two methyl carbon atoms C8 and C9 deviate by 0.389 (2) and -1.247 (1) Å, respectively, from this plane.
Cations and anions associate through intermolecular C-H···Cl hydrogen bonds. These two hydrogen bonds are run in opposite direction of the ab plane forming a helical shape arrangement ( Fig. 2 and Table 1). Intermolecular O-H···Cl, N -H···Cl and C-H···N interactions are also observed in the crystal structure (Fig. 3). In addition, the molecules are also connected by C-H···π interactions, the H3 atom (bound to C3) is at 2.87 Å from the centroid Cg1 i of the phenyl ring (symmetry code i = x, 1/2 -y, 1/2 + z), with a C3-H3···Cg1 i angle of 135° and a C3···Cg1 distance of 3.589 (2) Å.

Experimental
Commercially availbale hydroxylamine hydrochloride with p-dimethyl amino benzaldehyde was taken in equimolar ratio, were dissolved in double ethanol and stirred to yield a homogeneous mixture. The solution was allowed to evaporate at room temperature which yielded a brown crystalline salt. Single crystals were grown by slow evaporation from DMF.

Refinement
Atom H1N was located from a difference Fourier map and refined with a distance restraint of 0.89 (2) Å. The remaining H atoms were positioned geometrically and were treated as riding on their parent C and O atoms, with C-H = 0.93 Å and U iso = 1.2U eq (C) for aromatic H atoms, with C-H = 0.96 Å and U iso = 1.5U eq (C) for methyl H atoms, and with O-H = 0.82 Å and U iso = 1.2U eq (O).

Figure 1
The molecular structure of the title compound. Displacement ellipsoids are drawn at the 30% probability level    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.