The formation of [CH5O]+ and ions from the molecular ions of isobutyl alcohol

On the basis of field ionization kinetic and deuterium labelling experiments, it is shown that the molecular ions of isobutyl alcohol generate [CH5O]+ ions at 10−11 s via a 1,4‐shift of a hydrogen atom from one of the methyl groups to the oxygen atom, followed by a 1,2‐elimination of protonated methanol with a hydrogen atom of the other methyl group. At times > 10−11 s two distinct interchange processes between hydrogen atoms appear to compete with this reaction, as shown from field ionization kinetic experiments and metastable decompositions. Ion cyclotron resonance experiments on the long‐lived [CH5O]+ ions further demonstrate that they are protonated methanol ions. Arguments are put forward that the ions, generated by a specific 1,3‐elimination of a molecule of water from metastable decomposing molecular ions, have an isobutene structure.