ELECTRON-IMPACT MASS-SPECTRA OF POLYCYCLIC AROMATIC-COMPOUNDS WITH SEVERAL TYPES OF PYRIDINOBENZANTHRONE AND BENZOBENZANTHRONE SKELETONS

Electron impact mass spectra were measured for five isomers of pyridinobenzanthrones and three isomers of benzobenzanthrones. The fragmentation pattern and intensity of M2+, [M-H]+, [M-CO]i+, [M - CO - H(or 2H)]i+ and [M - CO - HCN]i+ (i = 1, 2) ions indicated remarkable differences and very interesting features according to the isomers with or without nitrogen and condensation positions of a pyridino or benzo ring to the benzanthrone skeleton. Further, the competition of decompositions through [M - H]+, [M - CO]+. or [M - HCN]+. ions was confirmed by the observation of metastable ions and the appearance energies of fragment ions. Interesting observations from these results were expulsion of an H atom in close proximity to the area around an O=C group, a weak bonding interaction between sp2 C-H and an O=C group, inducing specific hydrogen rearrangement, and characteristic charge localization on heteroatoms.