Far-infrared spectrum and ab initio calculations for vinylene carbonate

The far-infrared spectrum of vinylene carbonate shows five closely spaced b ands near 233 cm(-1), characteristic of a nearly harmonic ring-puckering po tential energy function. Using a coordinate dependent kinetic energy expans ion, the potential energy function was determined to be V (cm(-1)) = 1.652 X 10(5)x(2) - 1.416 X 10(5)x(4) where x is the puckering coordinate in Angs trom. This shows the molecule to be much more rigid than the similar 3-cycl openten-1-one due to pi bonding interactions involving the oxygen atoms adj acent to the carbonyl group. Ab initio calculations with a B3LYP/6-311 ++G* * basis set yield structural data in good agreement with the previous micro wave work and also predict vibrational frequencies that correspond closely to the experimental values. (C) 2000 Elsevier Science B.V. All rights reser ved.