MICROWAVE SPECTRUM AND ROTATIONAL ISOMERISM OF ETHYL FORMATE.

Abstract

The microwave spectra of two rotational isomers of ethyl formate have been analyzed. The conformation of both isomers shows the ethyl group to be cis with the doubly bonded oxygen. The dipole moment of the rotamer with the heavy atoms coplanar was found to be 1.98 D, and the dipole moment of the gauche form 1.81 D. The difference in zero-point energy between the two isomers has been determined by relative intensity measurements, and the results show the coplanar form to be favored by $177\pm 45$ calories. Five vibrationally excited states have been analyzed for the coplanar form, and one excited state for the gauche rotamer. The rotational constants and the relative intensities of these excited states will be discussed in terms of the potential function for the rotamers.