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The Elusive Formaldonitrone, CH2N(H)O. Preparation in the Gas Phase and Characterization by Variable-Time Neutralization−Reionization Mass Spectrometry, and Ab Initio and Density Functional Theory Calculations

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journal contribution
posted on 08.01.2000, 00:00 by Miroslav Polášek, František Tureček
Formaldonitrone, CH2N(H)O (1), the hitherto elusive simplest organic nitrone, has been prepared transiently in the gas phase by femtosecond collisional neutralization of its cation radical, CH2N(H)O+• (1+•). Ion 1+• was generated by dissociative ionization of 1,2-oxazolidine and characterized by collisionally activated dissociation mass spectra and augmented Gaussian 2(MP2) calculations. Nitrone 1 showed negligible dissociation upon collisional neutralization and was distinguished from its tautomers formaldoxime (2) and nitrosomethane (3). 1 was calculated to be more stable than its isomers CH2−O−NH (5) and oxaziridine (6). The enthalpy of formation of 1 was calculated from enthalpies of atomization and two isodesmic reactions as ΔHf,298(1) = 58 ± 1 kJ mol-1. The adiabatic and vertical ionization energies of 1 were calculated as IEa = 9.40 eV and IEv = 9.42 eV, the vertical recombination energy of 1+• was REv = 9.35 eV. Formation of 1 by collisional electron transfer was accompanied by negligible Franck−Condon effects. The potential energy surfaces for the formation, isomerizations, and dissociations of 1 and 1+• were investigated by ab initio calculations.