RING PUCKERING VIBRATION OF TRIMETHYLENE SULFOXIDE - FAR-INFRARED SPECTRUM FROM 50 TO 675 CM-1

A number of absorptions between 100 and 300 cm-1 in the infrared spectrum of trimethylene sulfoxide vapor have been observed and assigned to Δvp = 1 and 2 transitions in the ring puckering mode. With the aid of a computer program providing for a potential function essentially of the form V(x) = V2x2 + V3x3 + V4x4 (x the dimensioned puckering coordinate), the barrier to inversion between the stable equatorial and a possible axial conformer is established to be 1205 cm-1 with an uncertainty of ±11 cm-1 at the worst or ±1 cm-1 at best, depending upon the assignment of several very weak absorptions. The axial well depth, depending more critically upon these assignments, is no greater than 150 cm-1 and may be as low as 5 cm-1. © 1979.