Daniela Federsel, A. Herrmann, D. Christen
Jun 13, 2001
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0
Influential Citations
40
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Journal
Journal of Molecular Structure
Abstract
Abstract The geometric structure of α,α,α-trifluoroanisol, C6H5OCF3, was studied by gas electron diffraction (GED), microwave spectroscopy (MW), matrix infrared spectroscopy and quantum chemical methods. From the three experimental techniques, we conclude that only the perpendicular conformer (O–CF3 bond perpendicular to the benzene plane) is present in the gas-phase, although a slightly better fit of the GED intensities is obtained for a small contribution (12(8)%) of the planar form. Thus, the orientation of the O–CH3 bond in anisol changes from planar to perpendicular upon fluorination of the methyl group. The predictions of quantum chemical calculations for the conformational properties depend on the computational method and on the size of basis sets. HF/6-31G∗ and MP2 (6-31G∗ or 6-311(2d) basis sets) calculations predict the existence of a single conformer with perpendicular orientation, in agreement with our experimental data. The B3LYP method, however, results in a mixture of both conformers and HF/3-21G∗ calculations predict a single conformer with intermediate orientation.