Abstract: | The distonic ions HO+?CHCH2C˙H2 (1) and CH3C(?O+H)CH2C˙H2 (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 CH3CO+ and C2H5CO+ from 2 appear to be inversely proportional to the available excess energy. The 1,2-H-shift RC(?O+H)CH2C˙H2 → RC(?O+H)C˙HCH3 is compared to the corresponding, non-occurring 1,2-H-shift in alkyl free radicals. |