The farhyphen;infrared spectra arising from the two outhyphen;ofhyphen;plane ring vibrations of 1,3hyphen;oxathiolane have been recorded and analyzed. Fifteen pseudorotational (ringhyphen;bending) transition frequencies were observed in the 25ndash;125 cmminus;1region and were fit with the onehyphen;dimensional potential functionV(cmminus;1)=minus;541(1minus;costhinsp;2fgr;)+139(1minus;costhinsp;4fgr;). The molecule is twisted with a barrier to pseudorotation of 541plusmn;20 cmminus;1(1.54plusmn;0.06 kcal/mol). The spectra recorded include transition frequencies occurring above the barrier, and this is the first molecule (other than a nearly free pseudorotor) for which such bands have been seen. Seven radial transitions arising from three different pseudorotational states have also been observed in the 297ndash;317 cmminus;1region. Those in the pseudorotational ground state can be fit with a onehyphen;dimensional doublehyphen;minimum function with a barrier to planarity of 2720 cmminus;1. However, this value for the onehyphen;dimensional approximation is believed to be too high. Difference bands (180ndash;240 cmminus;1), sum bands (398ndash;426 cmminus;1), and double quantum transitions (144ndash;220 cmminus;1) were also detected and used to confirm the assignments.
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