Assignment of a Third Conformer of N-Methyl Ethylenediamine by Free-Jet Absorption Microwave Spectroscopy

The microwave spectrum of a third conformer (T2t) of N-methyl ethylenediamine has been assigned using a free-jet millimeter-wave spectrometer in the frequency range 60-78 GHz. T2t has an intermediate energy with respect to those of two conformers (T1 and T2g) previously assigned with conventional microwave spectroscopy [W. Caminati, A. C. Fantoni, and B. Velino, J. Mol. Struct. 157, 385-398 (1987)]. The assignment of the T2t conformer was missed in the previous MW investigation because of the very small value of the mu(a) dipole moment component.