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

Abstract

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⁺.