INVESTIGATION OF THE CONFORMATION AND ELECTRONIC-SPECTRA OF SIMPLE ORGANIC-MOLECULES BY THE NDDO METHOD

Calculations have been performed by using the semi-empirical all-valence-electron NDDO method for the molecules ethylene, formaldehyde, formyl fluoride, carbonyl fluoride, butadiene, acrolein, glyoxal, acryloyl fluoride, acrylic acid, glyoxalic acid and oxalic acid. The conformational stability of the conjugated systems were correctly reproduced with the exception of acrolein and acryloyl fluoride. The calculated dipole moments are in good qualitative agreement with the experimental values. It has been found that the ionization potentials are higher by a factor of 1.35 than the experimental ones. The singlet-singlet and singlet-triplet transition energies and oscillator strengths of ethylene, formaldehyde and formyl fluoride are presented. A factor of 1.46 is needed for good agreement with the experimental transition energies. © 1979.