Far‐infrared spectra and two‐dimensional potential energy surface for the out‐of‐plane vibrations of 2‐cyclopenten‐1‐one and its deuterated isotopomers Academic Article uri icon


  • The far‐infrared spectra of 2‐cyclopenten‐1‐one and its 5‐d1and 5,5‐d2derivatives have been recorded and analyzed. Each molecule has a ring‐puckering series of bands characteristic of mixed quartic–quadratic potential energy functions. The fundamental puckering frequencies were observed at 94.4, 89.0, and 84.9 cm−1, respectively, for the d0, d1, and d2species. In addition to the main puckering series for each molecule, side bands arising from the ring‐twisting excited states were also observed. Bands resulting from ring‐twisting transitions from various puckering states were observed for all three species in the 280–290 cm−1region. The data demonstrate that the molecular skeleton is planar. A two‐dimensional potential energy function of the form V=a1x41+b1x21+a2x42+b2x22+cx21x22, where x1and x2are the ring‐puckering and ring‐twisting 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.

citation count

  • 23

publication date

  • April 1991