Decomposition Channels Alternative to Remote-Charge Fragmentations Observed in Mass Spectrometry of Alkyltrimethylammonium Cations

A series of alkyltrimethylammonium cations, generated by fast atom bombardment from 1-dodecanaminium-, 1-tetradecanaminium- and 1-hexadecanaminium-N,N,N-trimethyl bromides, were studied by high-energy collisions and comparison with N,N,N-trimethyl-d9 labelled analogues. The results show that, together with remote-charge fragmentation processes, alkyltrimethylammonium cations exhibit further decomposition pathways which may be explained by interaction between the alkyl chain and the methyl group linked to the nitrogen atom. The sharp interruption of remote-charge fragmentation at the C-5 atom was observed for all compounds and explained as due to the formation of an energetically favoured six-membered cyclic structure.