An infrared investigation of Pyrrolidine-2-thione and -2-selenone

Abstract

Pyrrolidine-2-thione and -2-selenone together with their N-deutero and S- and Se-methiodide derivatives have been studied by i.r. spectroscopy over the range 4000-200 cm_-1. C=S and C=Se contribute to the bands at around 1000 cm^-1 and below 600 cm^-1. In pyrrolidine-2-selenone, the band at 1005 cm^-1 has been attributed to v(CSe). This value is the highest wave number for all similar pentaatomic rings, which we have previously investigated, and indicates a greater double-bond character in CSe. In the low-frequency region two bands at 497 and 334 cm^-1 in pyrrolidine-2- thione and two others at 352 and 280 cm^-1 in the selenium analogue are undoubtedly attributable to the C=S and C=Se modes respectively.