Microwave and far-IR spectra, conformational stability, molecular structure, barriers to internal rotation and ab initio calculations for the anticlinal conformer of trans-1-fluoro-2-butene

Durig, D. T.; Qiu, Howard Z.; Zhen, Mengzhang; Little, T. S.; Durig, J. R.

doi:10.1016/0584-8539(94)80171-1

Cited by 7 publications

(4 citation statements)

References 21 publications

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“…The bond distances and angles obtained from the MP2/6-31G* calculations are in much better agreement with those obtained from the microwave study [16]. The C-----C double-bond distance is calculated to be 1.336 and 1.338 tk in the cis and gauche conformers, respectively, which is the same as the value from the microwave study but 0.02 A longer than the RHF values.…”

Section: Ab Initio Calculationsmentioning

confidence: 68%

“…On the high-frequency side of this band a Q-branch is readily observable at 197.35 cm -~ as is one on the low-frequency side at 172.24 cm -~. Additionally, there is a well-defined Q-branch series beginning at 240 cm -~ which is assigned as the methyl torsional mode for the synclinal rotamer, This assignment is based on the methyl barrier previously determined [16] from the microwave spectrum of the gauche conformer. Using the V 3 of 596 cm -I, a harmonic approximation of the torsional frequency gives a value of 179 cm -I, whereas the V 3 calculated for the 172-cm -l Q-branch gives a value of 720 cm -l.…”

Section: Methyl Torsionmentioning

confidence: 97%

“…The energy minima with respect to nuclear coordinates were obtained by the simultaneous relaxation of all of the geometric parameters using the gradient method of Pulay [20]. The structural parameters, rotational constants, dipole moments, and energies for both the cis and gauche conformers determined with the RHF/3-21G, RHF/6-31G*, as well as the MP2/6-31G* basis sets are given in Table V along with the assumed values from the previous microwave investigation of the gauche conformer [16].…”

Section: Ab Initio Calculationsmentioning

confidence: 99%

“…We recently completed a microwave study [16] of trans-1-fluoro-2-butene, but we were only to assign the microwave spectrum of the gauche conformer. The major problem was not the fact that the cis conformer was not present but that we found it impossible to assign the b-type spectrum that arises from the cis conformer.…”

Section: Introductionmentioning

confidence: 99%

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Raman and infrared spectra, conformational stability, and ab initio calculations oftrans-1-fluoro-2-butene

Durig¹,

Herrebout²,

Qiu³

et al. 1996

Struct Chem

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The P, aman (3200 to 10 cm-i) and infrared (3200 to 20 cm-i) spectra of gaseous and solid trans-1-fluoro-2-butene, trans-CH3HC=CHCH2 F, have been recorded. Additionally, the Raman spectrum of the liquid with qualitative depolarization data has also been obtained. Variable temperature studies have been carried out with the sample dissolved in xenon. These spectral data have been interpreted on the basis that the molecule exists in the fluid phases as a mixture of the synclinal (fluorine atom oriented cis to the-double bond) and anticlinal (gauche) conformations and the synclinal conformer is more stable by 135 + 30 cm -I (377 + 106 cal/mol). There was a considerable scatter of the data but in the liquid state the anticlinal conformer is more stable and the only comformer present in the solid state. Ab initio gradient calculations employing the RHF/3-21G, PHF/6-31G*, and MP2/6-31G* basis sets predict the synclinal conformer to be more stable by 800, 86, and 150 cm -I, respectively. The fundamental asymmetric torsional mode for the synclinal comformer is observed at 123.9 cm -~ with three excited states falling to lower frequency. The corresponding mode for the anticlinal conformer is observed as a broad nondescript band centered at about 93 cm -I, Utilizing these data along with the AH and dihedral angle for the anticlinal conformer the potential function for the conformational interchange has been calculated. The determined coefficients are VI = -246 + 5, V 2 = 371 + 3, V 3 = 836 + 22, I/4 = 86 + 3, and V 6 = 85 + 8 cm-J. Complete equilibrium geometries for both conformers have been determined with the RHF/3-21 G, RHF/6-31G*, and MP2/6-31 G* basis sets. A normal coordinate analysis utilizing the harmonic force constants obtained with the MP2/6-3 IG* basis set has been carried out for both conformers. The results are discussed and compared with the corresponding quantities obtained for some similar molecules.

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Section: Ab Initio Calculationsmentioning

confidence: 68%

Section: Methyl Torsionmentioning

confidence: 97%