LOW-ENERGY FRAGMENTATIONS OF 5 ISOMERIC [H-3, C, N, O2] + . IONS

The low‐energy fragmentation characteristics of the [H3,C,N,O2]+· isomers [H3CNO2]+· (a), [H2CN(O)OH]+· (b), [H3CONO]+· (c), [HC(O)NHOH]+· (d) and [HC(OH)NOH]+· (e) were studied in detail by metastable ion mass spectrometry. In agreement with most earlier observations, appearance energy measurements established the potential energy surface of the isomers a, b and c, showing the intricate interrelations between them. It was concluded that a isomerizes into b prior to fragmentation by loss of ·OH and H2O and into c before loss of ·H and H3CO· moreover, the reverse reactions do not take place on the metastable time‐frame. The dominant metastable process for isomers d and e (obtained via HCN loss from glyoxime) was generation of [H2NOH]+·. For isomer e this process was proposed to involved a rate‐determining isomerization into d. It was concluded that isomers d and e do not intercommunicate with ions a, b and c prior to fragmentation. Neutralization‐reionization mass spectrometry indicated that the enol form of formohydroxamic acid as well as the keto counterpart are stable in the gas phase. Copyright © 1990 John Wiley & Sons, Ltd.