G2 Theory and Experiment in Concert: Enthalpy of Formation of CH3O-C=O+ and Its Isomers Revisited

Ab initio molecular orbital calculations at the Gaussian-2 level of theory on a set of isodesmic, atomization, and substitution type reactions have been used to deduce the enthalpy of formation of the methoxycarbonyl ion as ΔHf²⁹⁸[CH3O-C=O⁺] = 130 ± 2 kcal/mol. From the G2 computed ionization energy (IEa = 7.32 eV) and ΔHf²⁹⁸ (-40 kcal/mol) of the parent radical CH3O-C^•=O, we arrive at 129 kcal/mol for its ionic counterpart. Combining these …