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The reduced mass of the ring puckering motions for some four-membered ring molecules has been calculated based on the structural parameters obtained from ab initio geometry optimization calculations corresponding to a series of individual puckering angles. The dependence of the reduced mass on the puckering coordinate is considerably different from previous studies where the ring deformation and rocking parameter were assumed to be constant. By using the reduced mass function in the expression for the kinetic energy and Gaussian-polynomial potential function, the solutions of the ring puckering Hamiltonian reproduce the frequencies of hot bands of puckering transitions very well. Moreover, the puckering angle determined from this potential function agrees with the angle obtained from other structural studies.