Knowledge Bank

The rotational spectrum of N-methyl morpholine, [FIGURE], has been investigated in the 8 to 40 GHz region. Strong lines due to transitions of the equatorial methyl conformer have been assigned, giving rotational constants (in MHz) A = 4821.153 $\pm$ 0.061, B = 2342.574 $\pm$ 0.003 and $C=1719.453\pm 0.003(k=-0.598203)$ for the ground vibrational state. The barrier to methyl torsion, calculated from both the relative intensity and the A-E splitting of the v = 1 torsional satellite spectrum, is determined as $V3=1650\pm 200$ cal/mole. Vibrational satellites due to ring deformation modes have also been observed. The dipole moment components for the equatorial conformer are determined to be (in D) $\mu a=1.21\pm 0.02$, $\mu c=0.10\pm 0.03$ with $\mu total=1.21\pm 0.02.$ No lines due to the axial methy1 conformer have been assigned.