A SEMIRIGID BENDER ANALYSIS OF RING PUCKERING IN CYCLOPENTENE

The large-amplitude ring puckering vibration of cyclopentene has been investigated using the semirigid bender model. The structure of the molecule throughout the puckering motion was defined by assuming the atoms follow minimum potential energy paths, derived from ab initio molecular orbital predictions. The double-minimum potential function, determined by fitting rotational and vibrational spectra, has a barrier to planarity of 230 cm-1 and a ring puckering angle of 25.4°. This method of combining ab initio predictions with the semirigid bender method is suitable for modeling large-amplitude vibrational motion of nonrigid molecules with substantial energy barriers and has the advantage of more accurately locating the potential minima. © 1991.