Spectra and Structure of Perfluorocyclobutane

Abstract

Perfluorocyclobutane has been re& examined in an attempt to determine more definitely the question of whether or not the ring is planar. The infrared spectrum of the gas has been obtained under higher resolution and has been extended to 33 cm⁻¹. Two new fundamentals have been found, at 283 and 198 cm⁻¹, and the observed fundamentals have been classified as perpendicular or parallel on the basis of band contours. Infrared and Raman spectra of the liquid have been obtained to facilitate identification of coincidences. The NMR spectrum has been measured from 25° to −102°C. An interpretation of the experimental results is given and the fundamental vibrational frequencies are tentatively reassigned, based on the convincing evidence for the nonplanar D_2d structure.