Mass spectrometric decomposition of N-arylbenzonitrilium ions

Authors:

• Rafał Frański,
• Maciej Adam Zalas,
• Sebastian Beck,
• Andreas Springer,
• Michael Linscheid

Abstract

In order to determine the structure of fragment ions formed as a result of the HNCO neutral loss from protonated 1,3,4-oxadiazoles, the following compounds have been studied by electrospray ionisation (ESI) mass spectrometry: 2-(4′-methoxyphenyl)-5-phenyl-1,3,4-oxadiazole (1), N-(4′- methoxyphenyl)-benzamide (2) and 4-methoxy-N-phenyl-benzamide (3). Collision-induced dissociation mass spectra taken for fragment ions derived from protonated 1-3, namely [1 + H-HNCO]⁺, [2 + H-H₂O] ⁺ (N-4′-methoxyphenyl-benzonitrilium ion, A) and [3 + H-H ₂O]⁺ (4-methoxy-N-phenyl-benzonitrilium ion, B) have shown that upon HNCO loss from protonated 1 formation of ion B is favored. As shown by accurate mass measurement, the methyl and CO groups are lost in the next fragmentation step. © 2004 Elsevier B.V. All rights reserved.