AB-INITIO AND DENSITY-FUNCTIONAL STUDY OF AZIDOACETONE

The structure, ionisation energies and vibrational spectrum of azidoac etone (N3CH2COCH3) have been calculated using ab initio and density fu nctional methods. We have carried out calculations for two conformers of acidoacetone (anti and gauche). Calculations for the singly ionised structure (N3CH2COCH3+) are also reported. The predicted energy diffe rence between the anti and gauche conformer of azidoacetone has been c alculated at several different theoretical levels and our best estimat ion for this barrier is 1.6 kcal mol(-1). Ab initio (HF and MP2) ionis ation energies based on Koopmans' theorem are in good agreement with r ecent photoelectron spectroscopy (PES) measurements. Density functiona l ionisation energies from highest occupied orbital energies are very dependent on the exchange-correlation potentials and are lower than th e experimental values. However, density functional ionisation energies calculated by taking ground-state energy differences are in very good agreement with experimental results. Vibrational frequencies are in g ood agreement with experimental data for azidoacetone and related mole cules. (C) 1997 Elsevier Science B.V.