High Resolution Infrared Spectroscopy of Strained Ring Compounds

Author Institution: Department of Chemistry, Cornell UniversityA series of small strained ring compounds is under investigation to explore the role of low frequency, large amplitude motions on vibrational mode couplings. High resolution infrared spectra of cyclobutane and cyclopentane in a molecular beam have been determined. The high resolution spectra reveal extensive vibrational mode coupling in both molecules. The spectrum of cyclobutane suggests that two qualitatively different mode coupling mechanisms are involved. Furthermore, the two different tunneling states of the ring puckering mode in cyclobutane have dramatically different mode coupling behavior. Cyclopentane undergoes a barrierless pseudorotation which invovles ring puckering motion. The comparison of cyclobutane and cyclopentane provides insight into the connection between molecular structure and mode coupling involving large amplitude modes. Preliminary results have also been obtained for the dimer of cyclopentane