N′-Hydroxypyridine-2-carboximidamide

The title molecule, C6H7N3O, is almost planar (r.m.s. deviation = 0.0068 Å) and adopts an E conformation about the C=N double bond. In the crystal, molecules are linked by pairs of strong N—H⋯N hydrogen bonds, forming inversion dimers with R 2 2(10) motifs. The dimers are further linked into C(3) chains through O—H⋯N hydrogen bonds.

The title molecule, C 6 H 7 N 3 O, is almost planar (r.m.s. deviation = 0.0068 Å ) and adopts an E conformation about the C N double bond. In the crystal, molecules are linked by pairs of strong N-HÁ Á ÁN hydrogen bonds, forming inversion dimers with R 2 2 (10) motifs. The dimers are further linked into C(3) chains through O-HÁ Á ÁN hydrogen bonds.
The title compound, (I), crystalizes with a single molecule in the asymmetric unit. This is in contrast to (E)-3-chloro-N′hydroxybenzene-1-carboximidamide, (II), (Sreenivasa et al., 2012) which crystalizes with two molecules in its asymmetric unit. Compound (I) adopts an E configuration across the C=N double bond, as the OH group and the benzene ring are on opposite sides of the double bond, while the H atom of the hydroxy group is directed away from the NH 2 group. This is similar as observed in (II). In the packing, the molecules are linked to one another through strong intermolecular N-H···N hydrogen bonds into R 2 2 (10) motifs forming inversion dimers. The dimers are further linked into C(3) chains through O-H···N hydrogen bonds.

Experimental
To a solution of 2-cyanopyridine (1 mmol) in ethanol was added triethyl amine (2.5 mmol) and hydroxyl amine hydrochloride, NH 2 OH.HCl (3.5 mmol). The reaction mixture was stirred at room temperature for 12hrs. (The reaction was monitored by TLC). The solvent was removed and the crude product was purified by column chromatography using hexane and ethyl acetate as the eluent.
Single crystals required for X-ray diffraction measurements were obtained from slow evaporation of the solution of the compound in a mixture of ethanol and dichloromethane (1:4).

Refinement
The hydrogen atoms attached to N and O were located in difference maps and refined isotropically. The remaining H atoms were positioned geometrically and refined using a riding model, with C-H = 0.93 Å with isotropic displacement parameters set to 1.2 times of the U eq of the parent atom.

N′-Hydroxypyridine-2-carboximidamide
Crystal data Primary atom site location: structure-invariant direct methods Secondary atom site location: difference Fourier map Hydrogen site location: inferred from neighbouring sites H atoms treated by a mixture of independent and constrained refinement w = 1/[σ 2 (F o 2 ) + (0.0379P) 2 + 0.8786P] where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.011 Δρ max = 0.19 e Å −3 Δρ min = −0.18 e Å −3 Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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.