FAR-INFRARED SPECTRA AND TWO-DIMENSIONAL RING-BENDING POTENTIAL ENERGY SURFACE OF 1,3-OXATHIOLANE

Author Institution: Texas A\&M University, College Station; Pan American University, College StationThe far-infrared spectra of the five-membered ring 1,3-oxathiolane have been recorded and analyzed. A series of well-defined bands due to the ring-bending (hindered pseudorotation) vibration originate at 110 $cm^{-1}$. These are separated by about 10 $cm^{-1}$ and extend down to 33 $cm^{-1}$. A second series of bands near 314 $cm^{-1}$ arise from the ring-twisting (radial) mode. Sum, difference, and combination bands between the twisting and bending vibrations have also been observed and these provide a definitive assignment for all of the low-lying energy states. The pseudorotational series can be fit using a one-dimensional periodic potential and a barrier to pseudorotation of 500 $cm^{-1}$. However, the two-dimensional potential surface derived for this molecule provides a more complete picture of the conformational energetics. The calculations were aided by the determination of the appropriate kinetic energy expansions for the two out-of-plane ring motions