2,2,2-Trifluoroethyl 4-methylbenzenesulfonate

In the crystal structure of the title compound, C9H9F3O3S, intermolecular C—H⋯O hydrogen bonds link the molecules along the c-axis direction. Also present are slipped π–π stacking interactions between phenylene rings, with perpendicular interplanar distances of 3.55 (2) Å and centroid–centroid distances of 3.851 (2) Å.

In the crystal structure of the title compound, C 9 H 9 F 3 O 3 S, intermolecular C-HÁ Á ÁO hydrogen bonds link the molecules along the c-axis direction. Also present are slippedstacking interactions between phenylene rings, with perpendicular interplanar distances of 3.55 (2) Å and centroidcentroid distances of 3.851 (2) Å .

Related literature
The title compound is a reactive electrophile and a useful intermediate in organic synthesis. For general background and the synthesis, see: Gøgsig et al. (2008). For a similar structure, see: Asano et al. (2009). For bond-length data, see: Allen et al. (1987).

Comment
Electrophilic reagents play an important role in the synthesis of organic compounds and are often used in the synthesis of organic intermediates. (Asano et al. 2009). The title compound, 2,2,2-trifluoroethyl 4-methylbenzenesulfonate, is a electrophilic vinylation reagent commonly used for the synthesis of compounds such as vinyl styrenes that in turn find use as valuable intermediates in the synthesis of fine chemicals and as precursors to functionalized polymers (Gøgsig et al., 2008).
We report here in the crystal structure of the title compound, 2,2,2-trifluoroethyl 4-methylbenzenesulfonate. In the molecule of the title compound ( Fig. 1), bond lengths (Allen et al., 1987) and angles are within normal ranges. An intramolecular C-H···O hydrogen bond (Table 1) results in the formation of a five-membered ring (C4/C5/S/O3/H4A). In the crystal structure, the weak intermolecular C8-H8···O1 hydrogen bond connects the molecules along the direction of the c axis ( Fig.   2). Also present are slipped π-π stacking interactions between phenylene rings with perpendicular interplanar distances of 3.55 (2) Å and centroid to centroid distances of 3.851 (2) Å (symmetry operator for the second molecule: -x, 2-y, -z).

Experimental
The title compound, 2,2,2-trifluoroethyl 4-methylbenzenesulfonate was prepared on a literature procedure (Gøgsig et al., 2008). 2,2,2-Trifluoroethanol (19.90 mmol) and triethylamine (71.70 mmol) were dissolved in dry dichloromethane (20.0 mL). The solution was cooled to 273K and tosyl chloride (24.9 mmol) was added. The reaction was stirred at 273K for 1 h before being allowed to warm to room temperature. Hereafter the reaction was stirred at room temperature overnight. The organic phase was washed with brine (2 × 50 mL) and dried over sodium sulfate. After concentration in vacuo the crude product was purified by flash cromatography on silica gel using pentane/dichloromethane (4:1) and pentane/dichloromethane (3:1) as the eluents. This afforded of the title compound (96 % yield) as a colorless solid. Crystals suitable for X-ray analysis were obtained by slow evaporation of a methanol solution.

Refinement
H atoms were positioned geometrically, with C-H = 0.93, 0.98 and 0.96 Å for aromatic, methylene and methyl H, respectively, and constrained to ride on their parent atoms, with U iso (H) = xU eq (C), where x = 1.5 for methyl H and x = 1.2 for all other H atoms. Fig. 1. The molecular structure of the title molecule, with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.

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.