NORMAL-COORDINATE ANALYSES, VIBRATIONAL ASSIGNMENTS AND BARRIER TO INTERNAL-ROTATION IN ISOCYANATOACETALDEHYDE BASED ON AB-INITIO CALCULATIONS

The structure and conformational stability of isocyanatoacetaldehyde w ere investigated using ab initio calculations. The calculations were c arried out at RHF/6-311G and MP2/6-311G* levels. From the calculation the molecule was predicted to exist predominantly in the cis-cis conf ormation. The potential function for the internal rotation of the CHO group was determined for the molecule. The inclusion of electron corre lation into the calculations had a very small effect on the calculated potential coefficients. The vibrational frequencies were computed at the Hartree-Fock level. Normal coordinate calculations were carried ou t and potential energy distributions were calculated for the cis-cis c onformer of the molecule. The calculated vibrational frequencies for t he two conformers were scaled and compared to those observed experimen tally for similar molecules. (C) 1998 Elsevier Science B.V. All rights reserved.