Infra-Red and Raman Spectra of Polyatomic Molecules. V. Cyclopropane and Ethylene Oxide

Abstract

The Raman and infra‐red spectra of cyclopropane and ethylene oxide have been examined. The infra‐red spectra were examined using a potassium bromide prism from 25 to 11μ, a rock‐salt prism from 15 to 7μ and a fluorite prism from 8 to 1.5μ. Because of the greater dispersion of fluorite more bands than had previously been observed were resolved in the region in which this prism could be used. The nature, symmetry and selection rules of the vibrations of these two molecules are summarized. It was found possible to make a complete assignment of the fundamental frequencies of cyclopropane which accounts for all the features of the spectra. With ethylene oxide it was only possible to make a partial assignment. The frequencies of the corresponding fundamental modes of vibration of the two molecules are compared. On the basis of the frequency assignment described, values for the free energy, entropy and heat capacity of cyclopropane are calculated between 100° and 1000°K.