Reactivity of anomeric 1?- and 1?-pentofuranosyl azide derivatives in ammonia chemical ionization

Autor: Jože Kobe, Bogdan Kralj, Darko Kocjan
Rok vydání: 2001
Předmět:
Zdroj: Rapid Communications in Mass Spectrometry. 15:551-562
ISSN: 1097-0231
0951-4198
DOI: 10.1002/rcm.267
Popis: Electron impact (EI), fast atom bombardment (FAB) and ammonia chemical ionization [CI(NH3)] mass spectrometry were applied with the aim of differentiating between the anomeric 1α- and 1β-azidopentofuranosyl derivatives. Calculated ammonium affinities [AA(M)] and proton affinities [PA(M)] show that β-anomers have higher affinities for H+ and NH4+ ions than α-azides. Protonated molecules, obtained by CI(NH3) of azidofuranosyl derivatives, lose HN3 giving abundant furanosyl (S+) ions. Ammonia solvation of MH+ ions competes with the previous reaction producing the [SNHN2NH3]+ ion, a competitive product to the ammonium-attached [SN3NH4]+ ion. The fragmentation pathways of the stable and metastable [MNH4]+, MH+ ions, and several other important fragment ions, were determined using mass analyzed ion kinetic energy spectrometry (MIKES). The abundance of the [SN3NH4]+ and/or [SNHN2NH3]+ ions was found to correlate inversely with the exothermicity of ammonia solvation of the MH+ ion. The abundance of the fragment ions [SNHNH3]+, [SNH3]+ and SNH+ in some examples correlates with the exothermicity of the corresponding [MNH4]+ and MH+ parent ion formation. The fragment ions SNH3+ and SNHNH3+ can be formed, at least in part, in the ammonia solvation reaction of the S+ and SNH+ ions taking place within the high-pressure region of the CI ion source. Copyright © 2001 John Wiley & Sons, Ltd.
Databáze: OpenAIRE
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