Infrared Band Progressions in the CH2 Scissoring Region and the Ring Puckering Vibration of Trimethylene Oxide and some Deuterated Analogs

Abstract

Band progressions have been observed in the CH2 scissoring region of the i.r. spectra of trimethylene oxide (C3H6O) and three of its deuterated analogs (α-d2, β-d2, and α,α′-d4). With the aid of the pure ring puckering transitions (published previously) and a simple theoretical model of puckering–vibrational interactions the absorptions have been assigned to combination tones of CH2 scissoring vibrations with the ring puckering mode and its overtones. The scissoring fundamentals of the α- and β-methylene groups have been identified and assigned. Of all the vibrations for which combination progressions are observed, only the β-CH2 scissoring mode of the normal compound exhibits significant differences between the ring puckering transitions in the ground state and the vibrational excited state.