An investigation of structural stability and analysis of vibrational spectra of formyl ketene based on ab initio calculations

The conformational behavior and structural stability of formyl ketene were investigated by utilizing ab initio calculations with 6-311 ++G** basis set at restricted Hartree-Fock (RHF) and density functional (DFT-B3LYP) levels. The molecule was predicted to have the s-cis mutually implies s-trans conformational equilibrium. Full optimization was performed at the transition state and the rotational barrier was calculated. The π-π interaction between the carbonyl and ketene groups was found to stabilize the planar s- cis and s-trans conformers only with a relatively high rotational barrier. The vibrational frequencies were computed at the RHF and DFT-B3LYP levels and the zero-point corrections were included into the calculated rotational barrier. Complete vibrational assignments were made on the basis of normal coordinate calculations for both stable conformers of the molecule. (C) 2000 Elsevier Science B.V.