Vibrational spectra and rotational isomerism of allyl amine

Abstract

The infrared spectra of allyl amine in the vapour, liquid and solid phases have been measured from 250 to 4000 cm⁻¹. The laser-Raman spectrum in the liquid state has also been recorded photoelectrically and qualitative depolarization measurements have been made. The interpretation of the spectral data suggests the presence of two rotational isomers ('cis and trans", and 'ganche and trans') in the vapour and liquid phases whereas the form having asymmetrical structure ('gauche and trans', C₁ symmetry) gets stabilized in the solid state at low temperature. It is deduced from the shifts of some of the bands in various solvents (CCl₄, CH₃Cl, CH₃CN ete.) and in different physical states that a weak molecular association is present in both the liquid and solid states caused by inter-molecular hydrogen bonding effects. The strong and broad band at 3170 cm⁻¹ in the solid spectrum has been interpreted as resulting primarily from the associated N∃ H∃ N bond. A vibrational assignment for the observed bands has been attempted, keeping in view the presence of two rotational isomers in the vapour and liquid phases.