Neutralization-Reionization Mass Spectrometry. Distonic Oxonium and Ammonium Radical Ions

摘要

The distonic radical ions CH2CH2X(+)H, CH2CH2CH2X(+)H, CH2CH2CH2CH2X(+)H, where X = hydroxide or amine and their molecular ion counterparts HRX(+) have been studied with isotopic labeling and mass spectra produced by neutralization-reionization (NR) and collisionally activated dissociation (CAD). The isomerization HRX(+) yields RX(+)H is more exothermic for X = OH, but has a lower activation energy for X = NH2. For this reaction a 1,5-hydrogen rearrangement is favored over 1,4-H and the 1,3-H and 1,2-H rearrangements were not observed. NR spectra are particularly valuable for characterizing the distonic RX(+)H ions, as neutralization produces an unstable hypervalent species. CAD spectra of larger RX(+)H and HRX(+) ions are very similar; activation of RN(+)H3 mainly causes isomerization to HRNH2(+) which dissociates by alpha cleavage, the lowest energy pathway. Keywords: Neutralization-reionization mass spectrometry, Alkanes.