Cyclopropylidenemethanone: A Quasi-Symmetrical Molecule

Article abstract of DOI:10.1021/ja00337a012

The structure of cyclopropylidenemethanone has been investigated via microwave spectroscopy.Analysis of the spectra of the ground and nine excited vibrational states has revealed the form of two bending potentials involving motion of the methanone group relative to the cyclopropylidene ring.The vibration perpendicular to the plane containing the ring carbon atoms has a double-minimum potential with the ground state lying just 2 cm^-1 below the 29 cm^-1 high central barrier.Analysis of this motion using the rigid bender method shows that the two potential minima lie 17.5 deg away from the ring plane.The proximity of the ground state to the top of the barrier leads to the designation of the molecule as quasi-symmetric, being close to C_2ν, despite its less symmetric C_s equilibrium structure.The vibration in the plane of the ring has a near harmonic potential, with a fundamental of 154 cm^-1.Analysis of the Stark effect indicates a dipole moment of 2.60(1) D.