Spectra and structure of small ring compounds: Microwave spectrum, structure, and dipole moment of 1,1,2,2-tetrafluorocyclobutane

Abstract

The microwave spectrum of 1,1,2,2-tetrafluorocyclobutane, C 4H 4F 4, has been recorded from 26.5 to 40.0 GHz. The molecule is a b-type rotor. The R-branch assignments have been made for the ground state and four vibrationally excited states. Excited states of the CF 2 bending and the ring puckering modes have been assigned. Splitting was observed in the excited state of the ring puckering mode indicating that the molecule is puckered. From intensity measurements, the frequency for the 2 ← 0 and 3 ← 1 ring puckering transitions was calculated to be 80 ± 15 cm −1. The dipole moment was determined by the Stark effect to be μ b = 3.17 ± 0.03 D.