The distonic ions HO + CHCH 2 C ˙ H 2 and CH 3 C(O + H)CH 2 C ˙ H 2

The distonic ions HO + CHCH 2 C ˙ H 2 (1) and CH 3 C(O + H)CH 2 C ˙ H 2 (2) were directly generated, their decompositions characterized and their appearance energies determined by photoionization. Heats of formation derived from the appearance energies were 757 kJ mol −1 for 1 and 692 kJ mol −1 for 2. Deuterium labeling demonstrates that both ions decompose at low energies in the same ways as their isomers with the same skeletal structures, consistent with proposals that 1 and 2 are intermediates in the decompositions of those systems. Surprisingly, the values of the translational energy releases accompanying the formation of CH 3 CO + and C 2 H 5 CO + from 2 appear to be inversely proportional to the available excess energy. The 1,2‐H‐shift RC(O + H)CH 2 C˙H 2 → RC(O + H)C˙HCH 3 is compared to the corresponding, non‐occurring 1,2‐H‐shift in alkyl free radicals.