Energetic consideration applied to the mass spectra of some aromatic compounds

It is shown that the ‘metastable’ mass spectra of a series of monosubstituted benzenes are consistent with reaction over the lowest available energy surfaces. The non-occurrence of some qualitatively possible decomposition pathways may therefore be used to place lower limits on the heats of formation of gaseous cations. Conversely, where characterized reactions are preempted by new reactions upon introduction of additional substituents, upper limits may be placed upon the heats of formation of the ionic products of the new reactions. The concepts are employed to deduce that C₃H₆ elimination from n-butylbenzence subsequent to ionization leads to ionized toluene rather than ionized methyleneclohexadience.