Abstract
The conformations of several cyclic and bicyclic molecules were investigated through interpretation of their infrared and Raman spectra. The molecular systems included cyclopentene and three deuterated derivatives, a series of bicycle [3.2.0.] heptenes, methylcyclopropane, propylene oxide and propylene sulfide. As an extension of the bicycle-heptene series, tricycle [3.2.1.0. (superscript 1,5)] octane, a strained propellane, was synthesized and studied spectroscopically. The far infrared and the low-frequency Raman spectra of the three deuterated cyclopentenes were recorded, and the ring-puckering mode of each molecule was analyzed with a mixed quartic/quadratic potential energy function. The study revealed that, like cyclopentene (non planar, inversion barrier 232 cm⁻¹) the three deuterated derivatives have non-planar rings with inversion barriers of 231 cm⁻¹ (d₁), 224 cm⁻¹ (d₄) and 215 cm⁻¹ (d₈). In addition, the d₁ and d₄ molecules showed infrared active ring-twisting vibrations in the form of a series of closely spaced Q-branches for each molecule. Various models (with and without CH₂, CD₂ rocking) for the ring-puckering motion were considered in the one-dimensional calculations performed. The addition of methylene rocking into the puckering model slightly improved the observed/calculated frequency fit, but did not account for the decrease in barrier height with increasing deuteration. The dihedral angle obtained for each molecule was determined to be 26°..
Villarreal, John Ricardo (1976). An infrared and Raman study of some selected cyclic and bicyclic molecules. Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -614617.