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.