Crystal structure of pyrazoxyfen

The title compound, C20H16Cl2N2O3 (systematic name: 2-{[4-(2,4-dichlorobenzoyl)-1,3-dimethylpyrazol-5-yl}oxy}-1-phenylethan-1-one), is the benzoylpyrazole herbicide pyrazoxyfen. The asymmetric unit comprises two independent molecules, A and B, in which the pyrazole ring makes dihedral angles of 80.29 (10) and 61.70 (10)° and 87.60 (10) and 63.92 (8)°, respectively, with the dichlorophenyl and phenyl rings. In the crystal, C—H⋯O and C—H⋯N hydrogen bonds, and C—H⋯π and π–π [3.646 (2) Å] interactions link adjacent molecules, forming a two-dimensional network parellel to (011). In addition, the networks are linked by weak intermolecular C—Cl⋯π [3.356 (2), 3.950 (2), 3.250 (2) and 3.575 (2) Å] interactions, resulting in a three-dimensional architecture.


Related literature
For information on the herbicidal properties of the title compound, see: Hirai et al. (2002). For a related crystal structure, see: Indumathi et al. (2012).  Table 1 Hydrogen-bond geometry (Å , ).
Cg3 and Cg6 are the centroids of the C15-C20 and C35-C40 rings, respectively.  (Hirai et al., 2002). The asymmetric unit comprises two independent molecules, A and B, in which the dihedral angle between the dichlorophenyl and pyrazole and phenyl ring planes are 80.29 (10), 61.70 (10), 87.60 (10), and 63.92 (8)°, respectively. All bond lengths and bond angles are normal and comparable to those observed in similar crystal structures (Indumathi et al., 2012).

S2. Experimental
The title compound was purchased from the Dr. Ehrenstorfer GmbH Company. Slow evaporation of a solution in CH 3 CN gave single crystals suitable for X-ray analysis.

S3. Refinement
All H-atoms were positioned geometrically and refined using a riding model with d(C-H) = 0.95 Å, U iso = 1.2U eq (C) for aromatic C-H, d(C-H) = 0.99 Å, U iso = 1.2U eq (C) for methylene C-H and d(C-H) = 0.98 Å, U iso = 1.5U eq (C) for methyl C-H.  The asymmetric unit of the title compound with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms are shown as small spheres of arbitrary radius.

Figure 2
Crystal packing viewed along the a axis. The intermolecular interactions are shown as dashed lines.