Microwave Spectra of Nitrogen-Containing Molecules. II. Structure, Dipole Moment, Quadrupole Coupling Constants, and Barrier to Internal Rotation of N-Methyl Ethyleneimine

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Abstract
The microwave spectrum of N‐methyl ethyleneimine has been studied in the region 8 to 28 GHz, and the following rotational constants have been obtained for the ground state: A=16443.15 MHz, B=7219.84 MHz, C=6152.69 MHz. Stark‐effect measurements led to dipole‐moment components of μa=0.07±0.02 D μc=1.234±0.015 D, and a total dipole moment of 1.236±0.02 D. Internal rotation splittings were observed in the v=1 torsional state and gave a barrier to internal rotation of 3462±35 cal/mole. The quadrupole coupling constants of 14N in the inertial axis system were found to be: χaa=3.35, χbb=0.63, and χcc=−3.98±0.02 MHz. The molecular structure has been described, and the previously mentioned results have been discussed with regard to other existing data. A tentative estimate has been made of the quadrupole coupling constants in the field‐gradient principal‐axis system.