Knowledge Bank

Microwave rotational spectra have been assigned for the ground vibrational state of the species of N-methylformamide in which the methyl group is cis to the oxygen atom. No spectra belonging to any other species have been identified. The transitions in the cis species are widely split into doublets and we have attributed the splitting to internal rotation of the methyl group. A least squares fit of 12 transitions gave the following parameters:$ A_{0} = 19.4843$ GHz, $B0=6.3301$ GHz, $C0=4.9048$ GHz, $I\alpha =3.04$ u $\backslash AA2,\theta a\alpha =50.13\circ$, and $V_{3} = 205 $ cal/mole. The dipole moment, as determined from the Stark effect, is $3.86\pm 0.02D$.