A NEW PROPOSAL FOR A UNIFORM TREATMENT OF INTERNAL MOTIONS IN SYMMETRICAL AND ASYMMETRICAL 5-MEMBERED RING MOLECULES

A system of curvilinear coordinates for five-membered ring molecules is introduced and discussed. In this system all internal motions of any (symmetric or asymmetric) five-membered ring molecule can be treated as Large Amplitude Motions (LAMs). Specific calculations of two-dimensional (ring-puckering, ring-twisting) potential functions for cyclopentene and silacyclopentene molecules are presented. As an example of an asymmetric five-membered ring molecule 2,3-dihydrofuran is discussed. All these calculations are based on the numerical construction of the Hamiltonian for internal motions. An adiabatic approach is used for separation of LAMs from Small Amplitude Vibrations (SAVs). © 1992.