Vibrational Spectra and Conformational Behavior of Cyclopropylcarbonyl Chloride

Abstract

The vibrational spectra of cyclopropylcarbonyl chloride have been recorded and analyzed with the aid of the infrared spectrum of the corresponding bromide. The compound exists as a mixture of two discrete rotational isomers in the vapor and liquid states, but not in the solid state. The relative stabilities of the two isomers were determined by measuring the intensity–temperature dependence of their carbon–chlorine stretching vibrations in both the vapor and liquid states. The S‐cis form is shown to be the more stable conformer in both the vapor and liquid states, but the S‐trans form is the more stable in the solid state. Highly oriented polycrystalline masses are obtained on freezing, further indicating that intermolecular forces are unusual in this compound.