5-Chloro-1-phenyl-1H-pyrazol-4-amine

In the crystal structure of the title compound, C9H8ClN3, amino–pyrazole N—H⋯N hydrogen bonds connect the molecules along the [010] direction; the chains interact with each other only by van der Waals-type interactions. The pyrazole and phenyl rings are inclined at a dihedral angle of 45.65 (6)°

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: RK2288).
The Fig. 1 shows the perspective view of I. Two planar fragments, pyrazole (maximum deviation 0.0025 (12)Å) and phenyl (0.0082 (13)Å) rings are inclined by 45.65 (6)°. This is quite a typical value, for 241 compounds with similar structural fragment (5-substituted pyrazole, non-o-substituted phenyl) found in the Cambridge Structural Database (Allen, 2002; ver. 5.32 of Nov. 2010, last update May 2011) mean value of the twist angle is around 43°, and such is also the median value. The NH 2 -group is quite significantly twisted with respect to the pyrazole ring plane, the dihedral angle between two planes is 48 (2)°.
In the crystal structure the relatively weak N4-H41···N2 i hydrogen bonds join 2 1 screw-related molecules into the C (5) chains along y-direction. Symmetry code: (i) -x, y-1/2, -z+1/2. There are no other specific interactions, so apparently the chains are organized into three-dimensional structure by van der Waals forces.

Experimental
The compound was synthesized by electrochemical reduction of 4-nitro-1-phenylpyrazole in diluted hydrochloric acid to corresponding hydroxylamine and its in situ nucleophilic transformation into 5-chloro derivative. The compound was separated from post-reaction mixture with low yield. (Tallec et al., 2000).

Refinement
Hydrogen atoms from NH 2 -group were found in the difference Fourier maps and freely refined with isotropic displacement parameters. All other hydrogen atoms were placed in idealized positions (C-H distance 0.93Å) and refined as a riding model with their U iso = 1.2U eq (C). Fig. 1. The molecular structure of title compound with the atom numbering scheme. The displacement ellipsoids are drawn at 50% probability level. Hydrogen atoms are depicted as spheres of arbitrary radius. 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 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.