Rotational spectrum and ab initio calculations of N-methylformamide

Abstract

The microwave spectrum of N-methylformamide has been investigated in the 18–40 GHz frequency range. The rotational spectrum of the conformer with the methyl group cis to the aldehydic oxygen has been assigned. Several rotational transitions of the A sublevel of the ground torsional state have been measured for both normal and N—D isotopic species. The V₃ barrier to the methyl group internal rotation has been obtained from the effective pseudo-defect of inertia. The dipole moment and the ¹⁴N quadrupole coupling constants have been determined. The results of ab initio calculations performed at the HF and MP2 levels are in agreement with the experimental data