A SEMIRIGID BENDER ANALYSIS OF RING-PUCKERING IN CYCLOBUTANE

The semirigid bender method has been used to fit vibrational frequencies associated with the ring-puckering mode of cyclobutane and cyclobutane-d8. Molecular orbital predictions were used exclusively to predict the puckering vibration path. The ability to accurately estimate a known potential function and structural and inertial parameters, determined experimentally from a combination of vibrational spectra, electron diffraction measurements, and rotational spectra (of cyclobutane-d1), demonstrates the success of the method. The commonly used series expressions for the vibrational path in the semirigid bender method are shown to adequately represent the molecular orbital predictions of the path followed by atoms during the large-amplitude puckering motion. © 1992.