COMMENTS ON THE INTERACTION OF ROTATION WITH HINDERED BENDING VIBRATIONS.

Abstract

The effect of the transformation which decouples the states of the hindered bending vibration of compounds such as methylenecyclobutane, cyclopentene, and trimethylene sulfide has been determined. The results show that the use of the vibrational dependence of the effective rotational constants for determining the hindering potential is justified only after significant corrections are applied to the constants for the non-rigid $v = 0$ and $v = 1$ states. These corrections, which depend on the matrix element coupling $v = 0$ and $v = 1$, the inversion splitting, and the effective constants, have been evaluated for the compounds mentioned using previously reported data. For cyclopentene, a mixed quartic-quadratic potential containing a barrier of $230 cm^{-1}$ has been determined which reproduces the corrected rotational constant variation and most features of the far infrared spectrum observed by Fateley. For methylenecyclobutane, a potential function of the same form containing a barrier of $130 cm^{-1}$ has been estimated from the inversion splitting and the corrected rotational constant variation.