Bifunctional even-electron ions. IV. Fragmentation behaviour of aliphatic methoxonium ions containing an additional carbomethoxy group

As for the corresponding hydroxonium ions, the methoxonium ions \documentclass{article}\pagestyle{empty}\begin{document}${\rm R} \!-\! \mathop {\rm C}\limits^ + ({\rm OCH}_2)\! -\! ({\rm CH}_2)_n \! - \! {\rm COOCH}_3 $\end{document} (n = 0−5), b, show as the main reactions those triggered by functional group interaction, but the overall decomposition rate is not much influenced. Loss of CH3OH is the general primary fragmentation, originating preferentially from the COOCH3 group. The lowest homologue (b0) shows loss of C3H4O as the main primary reaction, while b1 shows loss of CH2CO besides CH3OH loss. The subsequent fragmentations exhibit strong chain‐length dependence. Methoxy anion migration is observed as a general reaction mode of fragment ions which still contain the COOCH3 group. The fragmentation behaviour of a and b and of the corresponding methoxy‐substituted bifunctional ions has been compared, and general conclusions have been drawn.