GENERATION AND FRAGMENTATION OF DIDEHYDRONAPHTHALENE RADICAL CATIONS UNDER ELECTRON-IMPACT

The electron impact mass spectra of disubstituted naphthalenes (chloronitro, acetylnitrol dibromo and dinitro derivatives) and of two naphthalenedicarboxylic anhydrides were studied under high resolution and by means of linked (B/E) scans. They all generate didehydronaphthalene radical cation, C10H6+., in most cases with a very high abundance, so that a convenient route to these interesting species is provided. These isomeric ions were all seen to lose the same fragments, namely C2H2, C2H4, C3H3, C4H2 or C2H2 + C2H4. In three instances, mass-analysed ion kinetic energy spectrometric (MIKES) and collisional activation/MIKES experiments were carried out and no differences in fragmentation behaviour were detected. Hence these isomeric C10H6+. ions achieve some common structure either before or during the fragmentation.