2-Chloro-4-(1H-pyrazol-1-yl)-5-(trifluoromethyl)pyrimidine

The reaction of 2,4-dichloro-5-(trifluoromethyl)pyrimidine with 1H-pyrazole gave two structural isomers in a 1:1 ratio that were separable by chromatography. The title compound, C8H4ClF3N4, was the first product to elute and was characterized in the present study to confirm that substitution by the pyrazolyl group had occurred at position 4. The molecule (with the exception of the F atoms) is essentially planar, with a mean deviation of 0.034 Å from the least-squares plane through all non-H and non-F atoms. The bond angles in the pyrimidine ring show a pronounced alternating pattern with three angles, including those at the two N atoms being narrower, and the remaining three wider than 120°.

The reaction of 2,4-dichloro-5-(trifluoromethyl)pyrimidine with 1H-pyrazole gave two structural isomers in a 1:1 ratio that were separable by chromatography. The title compound, C 8 H 4 ClF 3 N 4 , was the first product to elute and was characterized in the present study to confirm that substitution by the pyrazolyl group had occurred at position 4. The molecule (with the exception of the F atoms) is essentially planar, with a mean deviation of 0.034 Å from the leastsquares plane through all non-H and non-F atoms. The bond angles in the pyrimidine ring show a pronounced alternating pattern with three angles, including those at the two N atoms being narrower, and the remaining three wider than 120 .
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: EZ2213).

Comment
The reaction of 2,4-dichloro-5-(trifluoromethyl)pyrimidine with 1H-pyrazole gave two structural isomers in a 1:1 ratio that were separable by chromatography. The title compound was the first product to elute and was characterized in the present study to confirm substitution by N-pyrazolyl group to have occurred at position 4 ( Fig. 1).

Refinement
All H atoms were placed in geometrically calculated positions (C-H 0.93 Å) and included in the refinement in riding motion approximation. The U iso (H) were set to 1.2U eq of the carrying atom. Fig. 1. Molecular structure of the title compound, showing 50% probability displacement ellipsoids and atom numbering scheme. H atoms are drawn as circles with arbitrary small radius.

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 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.