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.