Molecular Structures of Propargyl Alcohol and Propargyl Amine from Microwave Spectra

Abstract

PROPARGYL alcohol and propargyl amine are of particular structural interest, because they belong to the rare class of substituted derivatives of methanol and methylamine in which the only possibilities of rotational isomerism are those associated with the COH or CNH₂ groups. We have assigned microwave spectra for six isotopic forms of propargyl alcohol and for the normal form of propargyl amine. The moments of inertia show that the rotamers concerned are those in which the OH and both NH bonds occupy gauche positions, that is, subtend dihedral angles in the region of 60° with respect to the acetylenic group. In the alcohol, the properties of the potential function for internal rotation are reflected in the occurrence of spectra of molecules in a very low-lying excited state and in the occurrence of series of spectral lines with first-order Stark effects.