High-energy [C,H-3,N,O] cation radicals and molecules

[C,H-3,N,O] cation radicals and molecules corresponding to the less stable isomers were investigated by a combination of ab initio and density functio nal calculations, and collision-induced dissociation and neutralization-rei onization mass spectrometric measurements. The ions formed by loss of oxyge n from a nitromethane cation radical and loss of hydroxyl radical from prot onated nitromethane were identified as having the nitrosomethane structure (2(+.)). A novel rearrangement in the ethyl nitrite cation radical was foun d to result in an elimination of formaldehyde to produce 2t' but not isonit rosomethane, CH3ON+. (3(+.)). Dissociations of 2(+.) and 2 were investigate d by variable-time neutralization-reionization mass spectrometry. Cleavage of the C-N bond was found to occur in both the neutral and ion with compara ble rate constants. Ab initio calculations provided C-N bond dissociation e nergies that were very similar in 2 and 2(+.), 161 and 164 kJ mol(-1), resp ectively. The calculated heats of formation, adiabatic and vertical ionizat ion energies, and recombination energies are reported for six [C,H-3,N,O] i on and neutral isomers, formamide, nitrosomethane, isonitrosomethane, forma ldoxime, formaldonitrone, and oxaziridine. (C) 2000 Elsevier Science B.V.