Vibrational spectra and structure of small ring compounds: XVIII. 3-oxetanone

Abstract

The infrared spectrum of gaseous 3-oxetanone has been recorded from 33 to 4000 cm −1. The infrared and Raman spectra of the corresponding liquid sample have also been measured and the data are shown to be consistent with a planar molecule of C 2V symmetry. A vibrational assignment of the 21 fundamental modes is proposed which is based on the gas phase band contours, group frequency correlations, and depolarization values. A regular progression of Q-branches originating at 140 cm −1 has been attributed to the anharmonic ring-puckering vibration. The data were fitted with a two parameter potential function of the form V = 13.23 ( z 4+27.48 z 2), where z is the reduced ring-puckering coordinate for the planar molecule. In liquid 3-oxetanone, the ring-puckering vibration was assigned to a band at 167 cm −1 which shifted to 230 cm −1 upon crystallization. The significance of the shifts upon condensation is discussed. A short CO bond length, on the order of 1.19 ± 0.01Å, is indicated by the high frequency of the carbonyl stretching vibration.