Molecular structure and internal rotation in 2,3,5,6-tetrafluoroanisole as studied by gas-phase electron diffraction and quantum chemical calculations.

doi:10.1021/JP046975D

Paper

Molecular structure and internal rotation in 2,3,5,6-tetrafluoroanisole as studied by gas-phase electron diffraction and quantum chemical calculations.

Published Jan 20, 2005 · A. Belyakov, M. Kieninger, R. Cachau

The journal of physical chemistry. A

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Abstract

The geometric structure of 2,3,5,6-tetrafluoroanisole and the potential function for internal rotation around the C(sp2)-O bond were determined by gas electron diffraction (GED) and quantum chemical calculations. Analysis of the GED intensities with a static model resulted in near-perpendicular orientation of the O-CH3 bond relative to the benzene plane with a torsional angle around the C(sp2)-O bond of tau(C-O) = 67(15) degrees. With a dynamic model, a wide single-minimum potential for internal rotation around the C(sp2)-O bond with perpendicular orientation of the methoxy group [tau(C-O) = 90 degrees] and a barrier of 2.7 +/- 1.6 kcal/mol at planar orientation [tau(C-O) = 0 degrees] was derived. Calculated potential functions depend strongly on the computational method (HF, MP2, or B3LYP) and converge adequately only if large basis sets are used. The electronic energy curves show internal structure, with local minima appearing because of the interplay between electron delocalization, changes in the hybridization around the oxygen atom, and the attraction between the positively polarized hydrogen atoms in the methyl group and the fluorine atom at the ortho position. The internal structure of the electronic energy curves mostly disappears if zero-point energies and thermal corrections are added. The calculated free energy barrier at 298 K is 2.0 +/- 1.0 kcal/mol, in good agreement with the experimental determination.

Study Snapshot

2,3,5,6-tetrafluoroanisole has a near-perpendicular orientation of the O-CH3 bond and a wide single-minimum potential for internal rotation around the C(sp2)-O bond, with a barrier of 2.7 +/- 1.6 kcal/

PopulationOlder adults (50-71 years)

Sample size24

MethodsObservational

OutcomesBody Mass Index projections

ResultsSocial networks mitigate obesity in older groups.

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Paper

Molecular structure and internal rotation in 2,3,5,6-tetrafluoroanisole as studied by gas-phase electron diffraction and quantum chemical calculations.

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References

Citations

Synthesis of Janus All-Cis Tetrafluorocyclohexanes Carrying 1,4-Diether Motifs

This study introduces a new class of Janus fluorocyclohexane derivatives with 1,4-diether substituents, enabling versatile synthesis and applications in various fields.

Stereoelectronic Chameleons: The Donor-Acceptor Dichotomy of Functional Groups.

Stereoelectronic factors can cause functional groups to revert donor-acceptor properties by changing their orientation in space, leading to chameleonic behavior in common organic functionalities.

Conformational composition of meta- and ortho-fluoro(trifluoromethoxy)benzene as studied by vibrational spectroscopy

Meta-fluoro(trifluoromethoxy)benzene exhibits a mixture of orthogonal and planar conformers in gas, liquid, and amorphous solid phases, while ortho-fluoro(trifluoromethoxy)benzene exhibits only one orthogonal conformer in

Room temperature chirped-pulse Fourier transform microwave spectroscopy of anisole

The room-temperature chirped-pulse Fourier transform microwave spectrometer reveals anisole's vibrational ground state, first and second excited states, and confirms prior millimeter wave studies.

Quasielastic and inelastic neutron scattering study of methyl group rotation in solid and liquid pentafluoroanisole and pentafluorotoluene.

Methyl group rotation in solid pentafluoroanisole and pentafluorotoluene is governed by uniaxial rotational jumps, while in liquid form it is nearly barrier-free.