Ga. Guirgis et al., Far infrared spectrum, barrier to internal rotation, and ab initio calculations for 3,3,3-trifluoropropene, VIB SPECTR, 23(2), 2000, pp. 137-150
The far infrared spectrum of gaseous 3,3,3-trifluoropropene, CH2CHCF3, betw
een 350 and 30 cm(-1) has been recorded at a resolution of 0.10 cm(-1). The
torsional fundamental for the CF, rotor is observed at 83.52 cm(-1). There
are three and possibly four "hot bands", which accompany this fundamental
falling to lower wavenumbers with decreasing intensities. Utilizing these t
orsional data along with structural parameters obtained from MP2/6-311+ G**
ab initio calculations to calculate the kinetic constant F, the barrier to
internal rotation has been determined to be 630 +/- 10 cm(-1) (7.54 +/- 0.
12 kJ/mol) and the V-6 term is relatively small with a value of - 30 +/- 5
cm(-1) (-0.36 +/- 0.06 kJ/mol). These results are compared to the CH3 barri
er of propene as well as to those of several CF3 rotors. The harmonic force
fields, infrared intensities, Raman activities, and depolarization ratios
have been obtained from both ab initio RHF/6-31G*; and MP2/6-31G* calculati
ons and the results compared. Additionally, predicted quantities are compar
ed to the corresponding experimental values when appropriate as well as wit
h some corresponding results for some similar molecules. (C) 2000 Elsevier
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