FAR-INFRARED SPECTRA AND 2-DIMENSIONAL POTENTIAL-ENERGY SURFACE FOR THE OUT-OF-PLANE VIBRATIONS OF 2-CYCLOPENTEN-1-ONE AND ITS DEUTERATED ISOTOPOMERS
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abstract
The farinfrared spectra of 2cyclopenten1one and its 5d1and 5,5d2derivatives have been recorded and analyzed. Each molecule has a ringpuckering series of bands characteristic of mixed quarticquadratic potential energy functions. The fundamental puckering frequencies were observed at 94.4, 89.0, and 84.9 cm1, respectively, for the d0, d1, and d2species. In addition to the main puckering series for each molecule, side bands arising from the ringtwisting excited states were also observed. Bands resulting from ringtwisting transitions from various puckering states were observed for all three species in the 280290 cm1region. The data demonstrate that the molecular skeleton is planar. A twodimensional potential energy function of the form V=a1x41+b1x21+a2x42+b2x22+cx21x22, where x1and x2are the ringpuckering and ringtwisting coordinates, was determined. For all three isotopomers, this gives rise to calculated frequencies which are in excellent agreement with the observed values. The interaction term c is larger than in related molecules, reflecting the effects of asymmetry and conjugation. 1991, American Institute of Physics. All rights reserved.
