Free jet rotational spectrum and ab initio calculations of acetanilide

Abstract

Acetanilide has been investigated by free jet millimeter wave absorption spectroscopy. The rotational spectrum of the conformer with the methyl group anti to the phenyl group 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. All the atoms of the peptidic group and the carbon of the methyl group are coplanar to the ring. The V₃ barrier to the methyl group internal rotation has been obtained from the effective pseudo defect of inertia. The results of MP2 and B3LYP/6-31G* ab initio calculations are in agreement with the experimental data, but indicate two additional stable high energy conformers.