Spectroscopic studies of rotational isomerism in β-halogenopropionitriles

Abstract

The infrared and Raman spectra of β-fluoro-, β-chloro-, β-bromo-, and β-iodo-propionitrile have been obtained over the complete fundamental vibrational frequency range. Solid-state i.r. spectra have also been measured. The results show that each of these compounds exists as an equilibrium mixture of gauche and trans isomers. In all cases the gauche isomer is the more stable form in the liquid phase. Enthalpy differences have been determined for the chloro-, bromo-, and iodo-derivatives. A vibrational frequency assignment has been made for each of the isomers and this has been tested by application of the sum rules.