Far‐infrared spectra and two‐dimensional potential energy surface for the out‐of‐plane vibrations of 2‐cyclopenten‐1‐one and its deuterated isotopomers
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The farâinfrared spectra of 2âcyclopentenâ1âone and its 5âd1and 5,5âd2derivatives have been recorded and analyzed. Each molecule has a ringâpuckering series of bands characteristic of mixed quarticâquadratic potential energy functions. The fundamental puckering frequencies were observed at 94.4, 89.0, and 84.9 cmâ1, respectively, for the d0, d1, and d2species. In addition to the main puckering series for each molecule, side bands arising from the ringâtwisting excited states were also observed. Bands resulting from ringâtwisting transitions from various puckering states were observed for all three species in the 280â290 cmâ1region. The data demonstrate that the molecular skeleton is planar. A twoâdimensional potential energy function of the form V=a1x41+b1x21+a2x42+b2x22+cx21x22, where x1and x2are the ringâpuckering and ringâtwisting 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.
author list (cited authors)
Cheatham, C. M., & Laane, J.