FAR INFRARED-SPECTRUM, BARRIER TO INTERNAL-ROTATION, RO STRUCTURE, AND ABINITIO CALCULATIONS FOR ACETYL CYANIDE

The far-IR spectrum has been recorded from 50 to 360 cm-1 at a resolution of 0.10 cm-1 for acetyl cyanide, CH3C(O)CN. The fundamental methyl torsion is observed at 126.06 cm-1 from which a periodic barrier to internal rotation is calculated to be 400 cm-1 (1144 cal mol-1). Utilizing previously reported rotational constants for eight isotopic species, r0 structural parameters are determined. The fundamental vibrational frequencies, barrier to internal rotation, and structural parameters are obtained from ab initio Hartree-Fock calculations employing 3-21G, 6-31G and DZ basis sets. These calculated parameters are compared to the experimentally determined values as well as to the corresponding quantities for some similar molecules. © 1990.