Microwave Spectrum and Ring-Bending Vibration of 3-Oxetanone

Abstract

The microwave rotational spectrum of 3-oxetanone, O–CH2–C=O||,–CH2–has been observed and assigned for the ground vibrational state, the first five excited states of the ring-bending vibrational mode, and the two carbon-13 isotopically substituted species. The features of the microwave spectrum indicate that the molecule has a single-minimum ring-bending vibrational potential and consequently a planar equilibrium configuration. Approximate models for the ring-bending vibrational mode were set up and the vibrational potential function interpreted in terms of contributions from ring-angle deformations and torsional interactions. The 13C data were used to derive a partial substitution structure. With the carbonyl carbon being labeled Cβ, the structural parameters determined in this way were r(CαCβ)=1.522±0.002 Å,∠CαCβCα′=88.06°±0.15°.The moment equations for the hypothetically planar molecule were solved to give some indication of the remaining parameters. Stark effect measurements yielded the dipole moment as 0.887± 0.005 D for the common isotopic species in the ground vibrational state.