Abstract:

The mechanism of unimolecular ion decomposition reaction of acetanilide and p-aminoasetophenone has been studied from both the experimental and the theoretical aspects. Experimentally metastable peaks were determined by lined scan of magnetic field and electrostatic field in mass spectrometer. Decomposition pathway of the two compounds in mass spectrometer was obtained theoretically, on the basis of molecular orbital theory, ab initio calculations with the3-2l basis sets hate been used to investigate the variations of energy in reactions. Total energy difference (△E) between parent ion and decomposition product was obtained by calculation. Ac-cording to the principle of the stability of product and of favourable energy, the reaction of least △E is dominat in the competitive decomposition reactions. Calculated result and that, of analysis by mass spectrometry are in agreement.

Key words:  Unimolecular ion decompositions, Molecular orbital theory, Ab initio calculation, Mass spectroscopy, Acetanilide, p-aminoacetophenone