2,4,6-Trifluoroaniline

The title compound, C6H4F3N, is a fluoro derivative of aniline. The molecule shows non-crystallographic mirror symmetry. Bond lengths are normal. The C—C—C angles show some deviation from the expected ideal values by up to 5°, a finding which is in accordance with a similar structure in the literature. In the crystal structure H⋯F contacts and H⋯N contacts lead to the formation of sheets whose surfaces are made up by the hydrophobic phenyl rings.

The title compound, C 6 H 4 F 3 N, is a fluoro derivative of aniline. The molecule shows non-crystallographic mirror symmetry. Bond lengths are normal. The C-C-C angles show some deviation from the expected ideal values by up to 5 , a finding which is in accordance with a similar structure in the literature. In the crystal structure HÁ Á ÁF contacts and HÁ Á ÁN contacts lead to the formation of sheets whose surfaces are made up by the hydrophobic phenyl rings.

Comment
In a program focused on the synthesis of derivatives of phenylarsonic acid a number of substituted aniline-derivatives were chosen as starting materials. In order to compare the influence of an arsonic group on the geometry of these starting materials, the crystal structure of 2,4,6-trifluoroaniline was elucidated by means of single-crystal X-ray diffraction.
In the molecule (Fig. 1) the C-C-C angles deviate from the expected ideal value of 120° by up to 5°. Angles bigger than the expected value are invariably found at C atoms bonded to fluorine, the smallest angle being present on the C atom bearing the amino group. This finding is in agreement with the situation observed in 2,3,4,5,6-pentafluoroaniline (Gdaniec, 2007).
In the crystal structure hydrogen bonds between fluorine and the amino group are present. If contacts whose ranges fall 0.2Å below the sum of van der Waals radii of the respective atoms are taken into consideration, only one of the F atoms in ortho position to the amino group is participating in these intermolecular interactions. These connect the molecules into sheets parallel to [1 0 1]. The surfaces of these sheets are made up by the aromatic moieties ( Fig. 2 and Fig. 3). In terms of graph-set analysis (Etter et al., 1990;Bernstein et al., 1995) the N-H···F pattern should be assigned a C(5) descriptor on the unitary level while the remaining H atom on nitrogen participates in a cooperative chain of hydrogen bonds (N-H···N).

Experimental
The compound was obtained commercially from Fluorochem. Crystals suitable for X-ray diffraction studies were obtained upon cooling the compound to 4 °C in a fridge.

Refinement
All H atoms were located in a difference map and refined as riding on their parent atoms with U iso (H) values of 1.2 U eq (C) and 1.2 U eq (N).
Due to the absence of a significant anomalous scatterer in the molecule, the Flack parameter is meaningless. Friedel opposites were merged and the absolute structure parameter was removed from the CIF file. Fig. 1. The molecular structure of the title compound, with atom labels and anisotropic displacement ellipsoids (drawn at 50% probability level) for non-H atoms.