Trifluoroacetic Acid; r<sub>0</sub> -Structure, Partial Substitution Structure and Deuterium Nuclear Quadrupole Coupling Studied by Molecular Beam Microwave Fourier Transform Spectroscopy and by ab initio Calculations

Antolı́nez, Sonia; Alonso, José L.; Dreizler, H.; Sutter, D. H.

doi:10.1515/zna-1999-8-915

Cited by 8 publications

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“…For FA and FA dimer, the hybrid DFT geometries in Table agree closely with those obtained by others at this level of theory. , The present study reports the first hybrid DFT geometries for Tfa and Tfa dimer. These are similar to the values obtained at the MP2/6-31+G(d) level, , however, the hybrid DFT method predicts closer monomer−monomer contacts. The main differences are in the dimer O···H distance (5.7% less), the dimer O···O distance (3.4% less), and the monomer O−H distance (1% less).…”

Section: Resultssupporting

confidence: 87%

“…Results also include a geometry optimization carried out at the B3LYP/aug-cc-pVTZ level of theory (527 basis functions). The optimum equilibrium geometry has C s symmetry with one C−F bond eclipsing the Tfa carbonyl, as observed with the Tfa monomer and Tfa dimer . Other conformations of the CF 3 group led to negative frequencies for CF 3 rotation.…”

Section: Resultsmentioning

confidence: 69%

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The Formic Acid−Trifluoroacetic Acid Bimolecule. Gas-Phase Infrared Spectrum and Computational Studies

Keller

2004

J. Phys. Chem. A

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The gas-phase FT-IR spectrum of the formic acid−trifluoroacetic acid (FA−Tfa) hydrogen-bonded complex, or bimolecule, was obtained by numerical analysis of the FT-IR spectrum of a mixture of FA and Tfa vapors. Nineteen out of 24 vibrational modes predicted by ab initio frequency calculations to occur in the mid-IR range (400−4000 cm-1) were observed as well-defined absorbance peaks, with the other five occurring as complex or overlapped regions. Several hydrogen-bond-influenced vibrations of each monomer were identified, including CO stretching and COH in-plane and OH out-of-plane bending. These occurred at 1701, 1403, and 871 cm-1, respectively, for FA, and at 1774, 1325, and 942 cm-1, respectively, for Tfa. The hydrogen bond donated by Tfa in the bimolecule appears to be stronger than that in the Tfa dimer, while the FA-donated hydrogen bond is weaker than that in the FA dimer. Geometry optimization and vibrational frequency calculations were carried out at 21 levels of theory up to B3LYP/aug-cc-PVDZ. All levels of theory predicted an unsymmetrical complex, with hydrogen bond distances of 1.608 Å and 1.706 Å donated by Tfa and FA, respectively, and the corresponding O···O distances of 2.620 Å and 2.704 Å (B3LYP/aug-cc-PVDZ). These values differ from the symmetrical, or nearly symmetrical, structure derived from microwave spectra (Costain and Srivastava, J. Chem. Phys. 1964, 41, 1620−1627; Martinache et al. Chem. Phys. 1990, 148, 129−140). In agreement with previous experimental findings, the bimolecule was predicted to be more stable than either homodimer, with a calculated ΔH complexation of −14.2 kcal/mol (B3LYP/aug-cc-PVDZ). Mulliken population analysis predicted a polar complex with a transfer of 0.02−0.03 protons from Tfa to FA and a predicted dipole moment of 2.3−2.4 D, depending on the level of theory. The combined spectroscopic and computational evidence indicates that in this complex the Tfa-donated hydrogen bond is strengthened more than the FA-donated hydrogen bond is weakened.

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Section: Resultssupporting

confidence: 87%

Section: Resultsmentioning

confidence: 69%

The Formic Acid−Trifluoroacetic Acid Bimolecule. Gas-Phase Infrared Spectrum and Computational Studies

Keller

2004

J. Phys. Chem. A

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Trifluoroacetic Acid; r₀ -Structure, Partial Substitution Structure and Deuterium Nuclear Quadrupole Coupling Studied by Molecular Beam Microwave Fourier Transform Spectroscopy and by ab initio Calculations

Abstract: We report the assignment and analysis of all stable monosubstituted isotopomers of trifluoroacetic acid. The

Cited by 8 publications

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The Formic Acid−Trifluoroacetic Acid Bimolecule. Gas-Phase Infrared Spectrum and Computational Studies

The Formic Acid−Trifluoroacetic Acid Bimolecule. Gas-Phase Infrared Spectrum and Computational Studies

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Trifluoroacetic Acid; r0 -Structure, Partial Substitution Structure and Deuterium Nuclear Quadrupole Coupling Studied by Molecular Beam Microwave Fourier Transform Spectroscopy and by ab initio Calculations

Abstract: We report the assignment and analysis of all stable monosubstituted isotopomers of trifluoroacetic acid. The

Cited by 8 publications

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The Formic Acid−Trifluoroacetic Acid Bimolecule. Gas-Phase Infrared Spectrum and Computational Studies

The Formic Acid−Trifluoroacetic Acid Bimolecule. Gas-Phase Infrared Spectrum and Computational Studies

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Trifluoroacetic Acid; r₀ -Structure, Partial Substitution Structure and Deuterium Nuclear Quadrupole Coupling Studied by Molecular Beam Microwave Fourier Transform Spectroscopy and by ab initio Calculations