Vibrational Spectra and Structure of Four-Membered Ring Molecules. IV. 2-Bromocyclobutanone and 2-Bromo-2,4,4-trideuterocyclobutanone

The infrared and Raman spectra of 2-bromocyclobutanone and 2-bromo-2,4,4-trideuterocyclobutanone in the liquid state have been recorded. The far-infrared spectra of both compounds have also been recorded from 33–300 cm−1 in both the vapor and liquid states. The assignment of the 27 normal vibrations is given. The interesting ring-puckering vibration in 2-bromocyclobutanone has been observed at 153 cm−1 in the Raman spectrum and at 141.5 cm−1 in the infrared spectrum of the vapor. For the deuterium compound the corresponding absorption bands have been observed in the Raman and infrared spectra at 152 and 141 cm−1, respectively. The data indicate that the potential function governing this vibration is only slightly anharmonic. No evidence has been found for the conformers previously reported for this molecule.