Benzyl vs. tropylium ions in the decomposition of some alkylnitrobenzenes

The [NO 2 C 7 H 6 ] + ions generated from m ‐alkylnitrobenzenes have been shown to be different in their decomposition from those generated from p ‐alkylnitrobenzenes, even when the alkyl group is methyl and the departing fragment a hydrogen radical. Thus, in these cases even molecular ions of relatively high internal energy do not reversibly ring‐expand to cycloheptatriene structures. In addition, the [NO 2 C 7 H 6 ] + ions, assumed to be benzylic, do not ring‐expand to nitrotropylium ions at internal energies sufficient to cause subsequent loss of NO or NO 2 from the p ‐ and m ‐isomers, respectively.