Bifunctional even-electron ions. III. Fragmentation behaviour of aliphatic hydroxonium ions containing an additional carbomethoxy group

The primary and subsequent fragmentations of the bifunctional oxonium ions documentclass{article}pagestyle{empty}begin{document}${rm R} !-! mathop {rm C}limits^ + ({rm OH})! -! ({rm CH}_2)_n ! - ! {rm COOCH}_3 $end{document} (n = 0?5), a, are dominated by functional group interactions. Loss of CH₃OH is the only appreciable primary fragmentation of the higher homoiogues, but for the lowest homologue (a₀) this reaction is missing. Instead, CO loss is observed. The next homologue (a₁) shov.s loss of CH₂CO besides loss of CH₃OH. The mode of the subsequent fragmentations is dependent on the chain length separating the functional group, and formation of cyclic ions is typical of the fragmentation behaviour of a₂ and a₃. Evidence for proton transfer from the carbonyl oxygen to the methoxy group of a protonated ester group is presented.