[2-(4-Methylbenzoyl)phenyl](4-methylphenyl)methanone

The asymmetric unit of the title compound, C22H18O2, contains one half-molecule, the complete molecule being generated by the operation of a crystallographic twofold rotation axis. The carbonyl group and the two C atoms attached to it forms interplanar angles of 23.67 (7)° with the methyl-substituted phenyl ring and 50.74 (8)° with the central ring. In the crystal, molecules are linked into infinite chains along the b-axis direction by intermolecular C—H⋯O interactions, generating R 2 2(10) graph-set motifs.

The asymmetric unit of the title compound, C 22 H 18 O 2 , contains one half-molecule, the complete molecule being generated by the operation of a crystallographic twofold rotation axis. The carbonyl group and the two C atoms attached to it forms interplanar angles of 23.67 (7) with the methyl-substituted phenyl ring and 50.74 (8) with the central ring. In the crystal, molecules are linked into infinite chains along the b-axis direction by intermolecular C-HÁ Á ÁO interactions, generating R 2 2 (10) graph-set motifs.

Comment
Diketones are popular in organic synthesis, for their applications in biology and medicine. They are known to exhibit antioxidants, antitumour and antibacterial activities (Bennett et al., 1999). They are also key intermediates in the preparation of various heterocyclic compounds (Sato et al., 2008).
The crystal packing is stabilized by C-H···O intermolecular interactions. The molecules are linked into infinite chains along the b axis via C1-H1···O1 ii hydrogen bonds, generating the R 2 2 (10) graphset motifs (Bernstein et al., 1995). The symmetry code: (ii) x, -1+y, z (look Table 1). The packing view of the compound is shown in (Fig. 2).

Refinement
The hydrogen atoms were placed in calculated positions with C-H = 0.93-0.96Å and refined in the riding model with fixed isotropic displacement parameters: U iso (H) = 1.5U eq (C) for methyl atoms and U iso (H) = 1.2U eq (C) for the aryl atoms.

Special details
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 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.