4-[4-(Heptyloxy)benzoyloxy]phenyl 2-oxo-7-trifluoromethyl-2H-chromene-3-carboxylate

The title compound, C31H27F3O7, is a liquid crystal and exhibits enantiotropic SmA and nematic phase transitions. In the crystal, the the 2H-chromene ring system makes dihedral angles of 54.46 (17) and 7.79 (16)°, respectively, with the central benzene ring and 4-(heptyloxy)benzene ring. The three F atoms of the –CF3 group are disordered over two sets of sites, with an occupancy ratio of 0.62 (3):0.38 (3). The crystal structre features two pairs of C—H⋯O hydrogen bonds, which form inversion dimers and generate R 2 2(10) and R 2 2(30) ring patterns. C—H⋯O interactions along [100] and C—H⋯π interactions futher consolidate the packing, leading to a three-dimensional network.

The title compound, C 31 H 27 F 3 O 7 , is a liquid crystal and exhibits enantiotropic SmA and nematic phase transitions. In the crystal, the the 2H-chromene ring system makes dihedral angles of 54.46 (17) and 7.79 (16) , respectively, with the central benzene ring and 4-(heptyloxy)benzene ring. The three F atoms of the -CF 3 group are disordered over two sets of sites, with an occupancy ratio of 0.62 (3):0.38 (3). The crystal structre features two pairs of C-HÁ Á ÁO hydrogen bonds, which form inversion dimers and generate R 2 2 (10) and R 2 2 (30) ring patterns. C-HÁ Á ÁO interactions along [100] and C-HÁ Á Á interactions futher consolidate the packing, leading to a three-dimensional network.   Table 1 Hydrogen-bond geometry (Å , ).

Related literature
Cg1 and Cg2 are the centroids of the C12-C17 and C19-C24 rings, respectively.
The N,N-dicyclohexylurea formed was filtered off and the filtrate was diluted with dichloromethane (25 ml). This solution was washed successively with water (2 x 30 ml), 5% aqueous acetic acid (3 x 50 ml), water (3 x 50ml) and was then dried (Na 2 SO 4 ). The residue obtained on removal of solvent was chromatographed on silica gel and eluted with chloroform as an eluent. Removal of solvent from the eluate afforded a white solid material which was crystallized repeatedly from ethanol to get colourless blocks.

Refinement
The H atoms bound to carbon were positioned with idealized geometry using a riding model with d(C-H) = 0.93-0.97 Å.
All C-H atoms were refined with isotropic displacement parameters set to 1.2-1.5 U eq (C). The F1, F2, and F3 fluorine atoms of the -CF3 group were disordered over two sites and refined with site occupancy factors 0.62 (3)

Figure 1
Molecular structure of the title compound, showing displacement ellipsoids drawn at the 50% probability level. Only the major component of the disordered CF 3 group is shown.

Figure 2
Crystal packing of the title compound with hydrogen bonds drawn as dashed lines.

Figure 3
Packing of the title compound. C-H···π interactions are shown as dashed lines.  Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'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 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.