Unimolecular Equilibration of Isomeric Cation Radicals. Mechanism of Decomposition of Ionized Methyl Isobutyrate in the Gas Phase

Article abstract of DOI:10.1021/ja00531a013

The fragmentation of gaseous cation radicals of methyl isobutyrate has been investigated with the aid of ion cyclotron resonance, collisional activation, and field ionization kinetic techniques and by deuterium and 13C labeling and deuterium isotope effect measurements.The results lead to the conclusion that the loss of CH3^. is preceded by a slow hidden hydrogen transfer from a β-methyl group to the carbonylic oxygen atom, and the resulting ion has the structure of protonated methyl acrylate.The elimination of C2H4, resulting in the ionized enol of methyl acetate, takes place by three distinct multistep pathways, each involving hydrogen migrations and skeletal rearrangements.