Mass-spectrometric study of benzopyridofulvenes

The dissociative ionization of benzopyridofulvenes that differ with respect to the position of the nitrogen atom in the azafluorene ring and the position and character of the substituents in the molecule was investigated. It is shown that the characteristic peculiarities of the fragmentation of these compounds can be explained by cyclization processes in the step involving the formation of [M-R]+ ions, where R=CH3 and C6H5 and are the substituents attached to the exocyclic carbon atom. Calculations of the π-bond energies of the molecular ion and the fragments by the Pariser-Parr-Pople method confirm the energie favorability of the formation of rings in the [M-R]+ions. © 1982 Plenum Publishing Corporation.