1-(4-Chloro-2-fluoro-5-nitrophenyl)-4-difluoromethyl-3-methyl-1H-1,2,4-triazol-5(4H)-one

In the title compound, C10H6ClF3N4O3, the dihedral angle between the benzene ring and the triazolone ring is 59.9 (1)°, while the nitro substituent subtends an angle of 39.5 (1)° to the benzene ring plane. In the crystal, pairs of molecules form inversion dimers via C—H⋯O hydrogen bonds.

In the title compound, C 10 H 6 ClF 3 N 4 O 3 , the dihedral angle between the benzene ring and the triazolone ring is 59.9 (1) , while the nitro substituent subtends an angle of 39.5 (1) to the benzene ring plane. In the crystal, pairs of molecules form inversion dimers via C-HÁ Á ÁO hydrogen bonds.

Related literature
For background to applications of this class of compound, see: Ager & Polsz (1996). For the synthesis and the use of the title compound in the production of herbicides, see: Goudar (1998). For bond-length data, see: Allen et al. (1987).   Table 1 Hydrogen-bond geometry (Å , ).

Li Yang and Jun Liu Comment
The title compound is an important intermediate used to synthesize the herbicide Carfentrazone-ethyl. It can also be used to synthesize other herbicides (Goudar, 1998), which are of wide interest for application to the control of broadleaf weeds and sedges (Ager & Polsz, 1996). We report here the crystal structure of the title compound, (I), which is of interest to us in this field.

Experimental
The title compound, (I) was prepared by a method reported in literature (Goudar, 1998). Crystals were obtained by dissolving (I) (0.2 g) in acetone (50 ml) and evaporating the solvent slowly at room temperature over 10 d.

Refinement
All H atoms were positioned geometrically and constrained to ride on their parent atoms, with C-H = 0.93 Å for aromatic H and 0.96 Å for alkyl H, respectively. The U iso (H) = xU eq (C), where x = 1.2 for aromatic H, and x = 1.5 for alkyl H.

Computing details
Data collection: CAD-4 Software (Enraf-Nonius, 1985); cell refinement: CAD-4 Software (Enraf-Nonius, 1985  The molecular structure of (I), with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.   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.