Chemical Aspects of the Infrared Absorption Spectra of the Ethyl Halides

The infrared absorption spectra of ethyl chloride, ethyl bromide and ethyl iodide have been determined with a prism spectrometer between 1.5μ and 15μ. Eight experimentally observed fundamental frequencies have been selected which, together with their first harmonics and simple combinations, are shown to account for the entire spectrum. A type of vibration between atom pairs believed to represent the important feature of the motion of the atoms is suggested for each of these fundamentals. The shifts in the absorption maxima produced by the substitution of the different halogens together with absorption and Raman data of related compounds are used in selecting these types of vibration. The bearing of these hypotheses on problems in chemical kinetics is discussed.