Remarkable rearrangement–dissociation processes of gaseous protonated methyl formate involving ion–dipole complexes

Collision induced decarbonylation of 13C, 18O-labelled protonated methyl formate, HC(OH)O*C*H3, involves the loss of both CO (40%) and CO*; the intermediacy of proton-bound dimers and ion–dipole complexes is invoked to explain the mechanisms.