Formation threshold structures of some [C5H7O]+ ions: use of general schemes for estimation of heats of formation of gas-phase organic ions

Recently published correlations between heat of formation and structure of gas-phase ions have been used to assign formation threshold structures to [C5H7O]+ ions produced by methyl radical loss from molecular ions of mesityl oxide, 5-hexene-2-one, 3-methylcyclopentanone, and 2-cyclohexenol. An unambiguous structure assignment has been made for the [C5H7O]+ daughter ion from mesityl oxide. For the three other precursors two common formation-threshold structures consistent with the thermochemical data are proposed.