(2E,6E)-2,6-Bis(2,4,5-trimethoxybenzylidene)cyclohexanone

In the title compound, C26H30O7, one atom in the cyclohexanone ring is disordered over two positions with a site-occupancy ratio of 0.871 (6):0.129 (6). The dihedral angles formed between the mean plane through the six C atoms of the major component of the cyclohexanone ring and two benzene rings are 35.09 (10) and 34.21 (10)°; the corresponding angles for the minor component are 20.1 (2) and 19.5 (2)°. Both the major and minor disordered components of the cyclohexanone ring adopt half-boat conformations. In the crystal packing, intermolecular C—H⋯O hydrogen bonds connect the molecules into a three-dimensional network.

In the title compound, C 26 H 30 O 7 , one atom in the cyclohexanone ring is disordered over two positions with a siteoccupancy ratio of 0.871 (6):0.129 (6). The dihedral angles formed between the mean plane through the six C atoms of the major component of the cyclohexanone ring and two benzene rings are 35.09 (10) and 34.21 (10) ; the corresponding angles for the minor component are 20.1 (2) and 19.5 (2) . Both the major and minor disordered components of the cyclohexanone ring adopt half-boat conformations. In the crystal packing, intermolecular C-HÁ Á ÁO hydrogen bonds connect the molecules into a three-dimensional network.

Comment
The chemistry of chalcones has generated intensive scientific interest due to their biological and industrial applications.

Experimental
A mixture of cyclohexanone (0.5 mmol), 2,4,5-trimethoxybenzaldehyde (4 g) and dry ammonium acetate (0.78 g) was taken in 1:4:2 molar ratio in methanol and heated on water bath till the colour changes to reddish orange, then diethyl ether (50 mmol) was added. The mixture was allowed to stand for 24 h resulting in the formation of needle-shaped crystals. Yield: 60%. Mp: 170 °C.

Refinement
The H atoms bound to C11 and C13 were located in a difference map and then constrained to ride with the parent atoms with U iso (H) = 1.2U iso (C). The other H atoms were positioned geometrically. [C-H = 0.9300 to 0.9700 Å]. The C11-C12A, C11-C12B, C13-C12A & C13-C12B distances were restrained with to be equal. The distance between H1A and H13D, H20A and H11C were restrainted to be 2.01 Å.

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. supplementary materials sup-9