Far Infrared Spectrum and the Barrier to Internal Rotation in 1,1,1,2-Tetrafluoroethane

Danti, Alfred; Wood, J. L.

doi:10.1063/1.1729991

Cited by 32 publications

(10 citation statements)

References 4 publications

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“…'s result. The rotational barrier for CH 2 FCF 3 , CHF 2 CF 3 , and CF 3 CF 3 are also experimentally determined as 4.20 kcal/mol by Danti et al, as 3.40 kcal/mol by Eltayeb et al, and as 3.67 kcal/mol by Gallaher et al respectively. Our result for CHF 2 CF 3 is 0.4 kcal/mol higher, while CH 2 FCF 3 and CF 3 CF 3 are in good agreement with the experimental results.…”

Section: Resultsmentioning

confidence: 83%

Ab Initio Calculations and Internal Rotor: Contribution for Thermodynamic Properties S°₂₉₈ and C_p(T)'s (300 < T/K < 1500): Group Additivity for Fluoroethanes

1998

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Ab initio calculations are performed on nine fluorinated ethane compounds and thermodynamic properties (S°2 98 and C p (T)'s 300 < T/K < 1500) are calculated. Geometries of stable rotational conformers and transition states for internal rotation are optimized at the RHF/6-31G* (6-31G(d)) and MP2/6-31G* levels of theory. Harmonic vibrational frequencies are computed at the RHF/6-31G* level of theory. Potential barriers for internal rotations are calculated at the MP2/6-31G*//MP2/6-31G* level. Parameters of the Fourier expansion of the hindrance potential are tabulated. Standard entropies (S°2 98 ) and heat capacities (C p (T)'s, 300 < T/K < 1500) are calculated using the rigid-rotor-harmonic-oscillator approximation with direct integration over energy levels of the intramolecular rotation potential energy curve. Heats of formation are adopted from literature evaluation and BAC-MP4 ab initio calculations. Thermodynamic properties for fluorinated carbon groups C/C/F/H2, C/C/F2/H, and C/C/F3 are determined by existing thermodynamic group parameter of C/C/H3 and data on CH 2 FCH 3 , CHF 2 CH 3 , and CF 3 CH 3 , respectively: no fluorine or other halogen is on the methyl carbon adjacent to the carbon bonded to the fluorine(s). Six interaction terms in addition to the above groups are developed to account for repulsion and steric effects. Interaction terms are required to accurately estimate ∆H f °298 , S°2 98 , and C p (T)'s (300 < T/K < 1500) for fluoroethanes where fluorine(s) are on carbons adjacent to a carbon bonded to fluorine(s).

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Section: Resultsmentioning

confidence: 83%

Ab Initio Calculations and Internal Rotor: Contribution for Thermodynamic Properties S°₂₉₈ and C_p(T)'s (300 < T/K < 1500): Group Additivity for Fluoroethanes

1998

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“…1,1,1,2-Tetrafluoroethane. Danti and Wood reported the far-infrared gas spectrum of 1,1,1,2-tetrafluorethane. Ward et al .…”

Section: Resultsmentioning

confidence: 99%

“…c Using 6-311++G(3df,3p), 6-311++G(3d,3p), 6-311++G(3d,3p), and 6-311+G(3df) for CF 2 HCH 3 , CF 3 CFH 2 , C 2 F 5 H, and C 2 F 6 , respectively. d From refs , , , and 12 in order of increasing fluorine substitution.…”

Section: Resultsmentioning

confidence: 99%

Rotational Barrier for 1,1-Difluoroethane, 1,1,1,2-Tetrafluoroethane, Pentafluoroethane, and Hexafluoroethane: A Density Functional and ab Initio Molecular Orbital Study

Parra

Zeng

1998

J. Phys. Chem. A

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The structures and vibrational frequencies for eclipsed and staggered conformers of CF 2 HCH 3 , CF 3 CFH 2 , C 2 F 5 H, and C 2 F 6 have been calculated by using B3LYP and MP2 ab initio methods. A reassignment of the experimental IR spectra of CF 3 CFH 2 and C 2 F 6 is suggested. Relative electronic energies are determined with a number of basis sets. Electron correlation is included by means of Møller-Plesset perturbation methods up to the fourth order. Scaled vibrational frequencies are used to account for zero-point energy and thermal contributions to electronic energies. Temperature dependence of the rotational barriers is studied at 20 K intervals from 0 to 300 K.

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“…The low-resolution infrared and Raman measurements, in combination with earlier results, − are used to develop reliable assignments for all 18 vibrations. We also report integrated infrared band intensities and use our vibrational frequencies to calculate the ideal gas heat capacity for HFC 134a.…”

Section: Introductionmentioning

confidence: 99%

Rotational and Vibrational Spectroscopy and Ideal Gas Heat Capacity of HFC 134a (CF₃CFH₂)

Xu¹,

Andrews²,

Cavanagh³

et al. 1997

J. Phys. Chem. A

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The hydrofluorocarbon HFC 134a (CF3CFH2) is the primary replacement for the chlorofluorocarbon CFC 12 (CF2Cl2) in numerous applications, including automobile air conditioning and home and commercial refrigeration. Here we describe a comprehensive spectroscopic study of this molecule. Precise microwave frequencies and molecular constants have been obtained for the vibrational ground state with a pulsed-molecular-beam Fourier-transform microwave spectrometer. New isotopic ground-state microwave measurements have also been made to improve the ground-state structural determination. Infrared and Raman spectra have been obtained, and all 18 vibrations have been observed and assigned. A high-resolution (3 MHz) microwave-sideband CO2 laser and an electric-resonance optothermal spectrometer have been used to observe the molecular-beam infrared spectrum in the vicinity of the low-resolution gas-phase feature at 975 cm-1 assigned here and in some of the earlier studies as the ν15, A‘‘-symmetry, CH2 rock. Two nearly equal-intensity c-type bands are observed under high resolution with origins at 974.35 and 974.87 cm-1. The presence of two vibrational bands of A‘‘ symmetry is attributed to strong anharmonic mixing of the ν15 vibration with a nearby combination vibration. On the basis of our low-resolution infrared measurements, we identify the perturbing state as the 3ν18 + ν8 combination level. Finally, the experimental results are used to calculate the vibrational contribution to the heat capacity and are compared with the results of earlier experimental and theoretical work, including our own electronic-structure calculations using an HF/6-31G* basis set.

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Far Infrared Spectrum and the Barrier to Internal Rotation in 1,1,1,2-Tetrafluoroethane

Cited by 32 publications

References 4 publications

Ab Initio Calculations and Internal Rotor: Contribution for Thermodynamic Properties S°₂₉₈ and C_p(T)'s (300 < T/K < 1500): Group Additivity for Fluoroethanes

Ab Initio Calculations and Internal Rotor: Contribution for Thermodynamic Properties S°₂₉₈ and C_p(T)'s (300 < T/K < 1500): Group Additivity for Fluoroethanes

Rotational Barrier for 1,1-Difluoroethane, 1,1,1,2-Tetrafluoroethane, Pentafluoroethane, and Hexafluoroethane: A Density Functional and ab Initio Molecular Orbital Study

Rotational and Vibrational Spectroscopy and Ideal Gas Heat Capacity of HFC 134a (CF₃CFH₂)

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Far Infrared Spectrum and the Barrier to Internal Rotation in 1,1,1,2-Tetrafluoroethane

Cited by 32 publications

References 4 publications

Ab Initio Calculations and Internal Rotor: Contribution for Thermodynamic Properties S°298 and Cp(T)'s (300 < T/K < 1500): Group Additivity for Fluoroethanes

Ab Initio Calculations and Internal Rotor: Contribution for Thermodynamic Properties S°298 and Cp(T)'s (300 < T/K < 1500): Group Additivity for Fluoroethanes

Rotational Barrier for 1,1-Difluoroethane, 1,1,1,2-Tetrafluoroethane, Pentafluoroethane, and Hexafluoroethane: A Density Functional and ab Initio Molecular Orbital Study

Rotational and Vibrational Spectroscopy and Ideal Gas Heat Capacity of HFC 134a (CF3CFH2)

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Product

Resources

About

Ab Initio Calculations and Internal Rotor: Contribution for Thermodynamic Properties S°₂₉₈ and C_p(T)'s (300 < T/K < 1500): Group Additivity for Fluoroethanes

Ab Initio Calculations and Internal Rotor: Contribution for Thermodynamic Properties S°₂₉₈ and C_p(T)'s (300 < T/K < 1500): Group Additivity for Fluoroethanes

Rotational and Vibrational Spectroscopy and Ideal Gas Heat Capacity of HFC 134a (CF₃CFH₂)