Ionized pentanoic acid, 3-methylbutanoic acid, and theenol isomer of ionized isopropyl acetate are shown to pass in part through common intermediates before decomposing to CH3CHC (OH) 2+(7) and the “McLafferty+ ion CH3C (OH) 2+(10). The H transfer to form the methylof CH3C (OH) 2+ and the joining of two CH2 groups to form the CC bond in the ethylene eliminated to produce CH3CHC (OH) 2+ are both attributed to reactions of the ion-neutral complex [CH3CH= CH2 CH2C (OH) 2+]. The McLafferty+ 1 ion is also formed, especially from ionized esters, byanother pathway in which complexes may or may not be intermediates. The intermediacyof the ion-neutral complexes is supported by energetic considerations, isotope effects, and the decomposition patterns of labeled ions. The latter correlate with a preference for hydrogen transfer from the end carbons of the C3 partner in other reactionsproposed to be complex-mediated. Unification of the McLafferty rearrangement, the McLafferty+ 1 rearrangement, and the McLafferty rearrangement with charge reversal by a common initial-hydrogen rearrangement followed by dissociation or isomerization in ion-neutral complexes is proposed. Group migration by 1, 2-shifts, possibly by dissociation to form a double bond in one partner in an ion-neutral complex followedby addition at the opposite end of the double bond, is shown to be a general reaction of ions in the gas phase.