Organic Ions in the Gas Phase. IV. C7H7+ and C5H5+ Ions from Alkylbenzenes and Cycloheptatriene

Electron-impact studies have led to the proposal that the C7H7+ ion derived from toluene is not benzyl but tropylium. The mass spectra of toluene-α-C13 and cycloheptatriene confirm this proposal. Energy considerations indicate that toluene and related aromatic hydrocarbons yield the same kind of C7H7+ ion as cycloheptatriene, and that formation of this ion from toluene and cycloheptatriene proceeds through the same intermediate. A metastable peak, labeling, and correlations indicate that C5H5+ ions from n-alkylbenzenes are derived in part from a C7H8+ precursor, and not exclusively from C7H7+.