MICROWAVE-SPECTRUM, STRUCTURE, DIPOLE-MOMENT, AND INTERNAL-ROTATION OF CIS-AZOMETHANE

The microwave spectra of the ground state of cis-azomethane and of the ground and first excited torsional state of cis-azomethane-d0 have been observed and analyzed (for the excited torsional state, Q-branch assignment only). Values for r(C-N) and ∠CNN of 1.48 Å and 119.3°, respectively, are obtained from the rotational constants of these two isotopic species and an assumed r(N=N) of 1.254 Å. Analysis, neglecting possible top-top coupling, of the internal rotation splittings observed in the ground state transitions of the h6 species gives a barrier of 1320 cal/mol, with the uncertainty determined by the inadequacy of the model. This internal rotation analysis also gives an outward tilt of the methyl groups of 6.7 ± 3°. The dipole moment has been determined by measurement of the Stark effect to be 3.27 ± 0.1 D. © 1979 American Chemical Society.