Diethyl 2,2′-(ethane-1,2-diyldioxy)dibenzoate

The molecular title compound, C20H22O6, was obtained by the reaction of ethyl 2-hydroxybenzoate with 1,2-dichloroethane. The molecule lies on a twofold rotation axis which passes through the middle of the central ethylene bridge. This group exhibits a gauche conformation with the corresponding O—C—C—O torsion angle being 73.2 (2)°. The C atoms of the carboxyl group, the aryl and the O—CH2 group are coplanar, with an r.m.s. deviation of 0.01 Å. The two aryl rings form a dihedral angle of 67.94 (4)°. The ester ethyl group is disordered over two sets of sites with an occupancy ratio of 0.59 (2):0.41 (2). The crystal packing is dominated by van der Waals forces.

The molecular title compound, C 20 H 22 O 6 , was obtained by the reaction of ethyl 2-hydroxybenzoate with 1,2-dichloroethane. The molecule lies on a twofold rotation axis which passes through the middle of the central ethylene bridge. This group exhibits a gauche conformation with the corresponding O-C-C-O torsion angle being 73.2 (2) . The C atoms of the carboxyl group, the aryl and the O-CH 2 group are coplanar, with an r.m.s. deviation of 0.01 Å . The two aryl rings form a dihedral angle of 67.94 (4) . The ester ethyl group is disordered over two sets of sites with an occupancy ratio of 0.59 (2):0.41 (2). The crystal packing is dominated by van der Waals forces.

Related literature
For synthesis and structures of diesters, see: Ma et al. (2012); Hou & Kan (2007). For properties and applications of diesters, see: Chen & Liu (2002). For the synthesis of the title compound, see: Ma & Liu (2002). For standard bond lengths, see: Allen et al. (1987). For background to the applications of organic acids and esters, see: Chanthapally et al. (2012)

Comment
In recent years the chemistry of carboxylic compounds has been the subject of intense studies because of the potential applications of these compounds as ligands for metal complexes or of potential applications as luminescent, non-linear optical, electrical conductive and liquid-crystalline materials (Yan et al., 2012. Chanthapally et al., 2012. Esters are also very important since these compounds are commodity chemicals used as intermediates in the manufacture of acids and in the production of numerous important industrial products. Hence, the current work aims to synthesize new esters for acid production and for investigation of their coordination behaviors with metal ions (Ma et al., 2012;Chen & Liu, 2002).
Here, we report the crystal structure of a new diester, C 20 H 22 O 6 , which was obtained by reaction of ethyl 2-hydroxybenzoate with 1,2-dichloroethane.
The structure of C 20 H 22 O 6 consists of a neutral molecular unit (

Experimental
The title compound was obtained by the reaction of ethyl 2-hydroxybenzoate with 1,2-dichloroethane in N,N′-dimethylformamide (DMF) according to a reported procedure (Ma & Liu, 2002). In a 100 cm 3 flask fitted with a funnel, ethyl 2hydroxybenzoate (8.3 g, 50 mM) and potassium carbonate were mixed in 50 cm 3 of DMF. To this solution was added dropwise a stoichiometric quantity of 1,2-dichloroethane (2.5 g, 25 mM) dissolved in 20 cm 3 of DMF for a period of an hour under stirring. The mixture was further stirred for 24 h at 353 K. The solution was concentrated under reduced pressure and the white solid precipitated by adding a large quantity of water (200 cm 3 ) was filtered off and recrystallized from ethanol and decolored with activated carbon. A colorless solid was finally obtained (yield 81 %, m.p: 417-419 K).
Slow evaporation of a solution of the title compound in ethanol and dichloromethane (1:1) led to the formation of colorless crystals, which were suitable for X-ray characterization.

Refinement
All H atoms were positioned geometrically and refined using a riding model with C-H = 0.93 -0.97 Å and with U iso (H) = 1.2 times U eq (C) or 1.5 times U eq (methyl C). The two carbon atoms of the ethyl group are disordered over two sets of sites with an occupancy ratio of 0.59 (2):0.41 (2). The C atoms of this group were additionally refined with the ISOR command in SHELXL.   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 > 2sigma(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.

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