[C3H3O]+ ions; reacting and non‐reacting configurations

Abstract Three [C 3 H 3 O] + ion structures have been characterized. The most stable of these is $$ {\rm CH}_{\rm 2} = {\rm CH} - \mathop {\rm C}\limits^ + = {\rm O} $$ its heat of formation Δ H f was measured as 749±5 kJ mol −1 . In the μs time frame this ion fragments exclusively by loss of CO, a process which also dominates its collisional activation mass spectrum. The other stable [C 3 H 3 O] + structures, $$ {\rm CH}\equiv \mathop {\rm C}\limits^ + - {\rm CHOH} $$ and $$ {\rm CH}_{\rm 2} = {\rm C} = \mathop {\rm C}\limits^{\rm + } - {\rm OH}, $$ , were generated from some acetylenic and allenic precursor ions; their heats of formation were estimated to be 830 and 880 kJ mol −1 respectively. The former ion was also produced by the gas phase protonation of propynal. These ions show loss of C 2 H 2 and CO in both their metastable ion and collisional activation mass spectra. The broad Gaussian‐type metastable peak for the loss of CO was shown to consist of two components corresponding to gragmentations having different activation energies.