An investigation of the decomposition of the intermediate ions produced by electron-impact. II—[C7H7]+ ions from several halogenotoluenes

The structure and decomposition of the C₇H₇]⁺ ions produced by electron-impact from o-, m- and p-chlorotoluene, o-, m- and p-bromotoluence, and p-iodotoluence, have been investigated. By determining the relative abundance of normal and metastable ions, these C₇H₇]⁺ ions at electron energy of 20 eV are shown to be so-called ‘tropylium ions’. The amount of the internal energy of the C₇H₇]⁺ ion estimated by the relative ion abundance ratios, ? C₅H₅]⁺/C₇H₇]⁺ and m*/C₇H₇]⁺ for the decomposition \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm C}_{\rm 7} {\rm H}_{\rm 7}]^ + \mathop \to \limits^{m^* } {\rm C}_{\rm 5} {\rm H}_{\rm 5}]^ + + {\rm C}_{\rm 2} {\rm H}_{\rm 2} $\end{document}, is in the order iodotoluene > bromotoluene > chlorotoluene. The heats of formation of the activated complexes for the reaction \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm C}_{\rm 7} {\rm H}_{\rm 7}]^ + \mathop \to \limits^{m^* } {\rm C}_{\rm 5} {\rm H}_{\rm 5}]^ + + {\rm C}_{\rm 2} {\rm H}_{\rm 2} $\end{document} were estimated. The values suggest that the decomposing C₇H₇]⁺ ions from various halogenotoluenes are identical in structure.