Decomposition of Tropylium and Substituted Tropylium Ions

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Abstract
Metastable transitions arising from the decomposition of tropylium ions have been investigated in a double‐focusing mass spectrometer. It has been shown that the loss of an acetylene molecule is the only major decomposition process, and metastable peaks in the mass spectrum of toluene‐α‐d3 have been interpreted in terms of this. The relative intensities of the metastable peak and the normal peak at m/e=65 in the mass spectra of several compounds have been shown to correlate with the apparent heat of formation of the C7H7+ ion. Metastable transitions in the mass spectra of several halogenated and alkylated toluene and benzyl compounds have been interpreted in terms of the decomposition of substituted tropylium ions by the elimination of C2H2 or C2HX (X = F, Cl, Br). No evidence could be found for the existence of a pseudotropylium ion in which a CH group is replaced by a N atom in the mass spectra of alkyl pyridines.