Are benzoylium and nitrilium ions produced from substituted 2-arene-2-oxazolines during mass spectrometry? A study based on density functional theory calculations, quantum theory of atoms in molecules, and electrospray ionization tandem mass spectrometry

Author(s)

Borges, Leticia da Silva ; Carvalho Batista, Joao Henrique ; Bozzini, Leandro ; Lourenco Jr, Celso Donizete ; Lopes, Norberto Peporine ; Clososki, Giuliano Cesar ; Vessecchi, Ricardo

• Document type: Journal article
• Source: RAPID COMMUNICATIONS IN MASS SPECTROMETRY; v. 37, n. 4, p. 11-pg., 2023-02-28.

Abstract

RationaleOxazolines are important compounds for drug development, synthesis, and pharmaceutical applications. Interest in analyzing and developing methods to characterize reaction products from these small heterocyclics has led us to study the gas-phase reactivity and fragmentation of seven 2-arene-2-oxazolines compounds using computational chemistry combined with mass spectrometry. MethodProtonation sites were investigated using computed proton affinity, gas-phase basicity, and some quantum chemistry descriptors of reactivity; the B3LYP/6-31+G(d,p) computational model was used. Fragmentation mechanisms were suggested by employing data from collision-induced dissociation (CID), energy-resolved plots from MS/MS spectra, multiple-stage experiments, and survival-yield method. ResultsProtonation studies based on quantum theory of atoms in molecules (QTAIM) and computational thermochemistry were useful to describe the reactivity of the investigated 2-arene-2-oxazolines, which can be protonated at the nitrogen atom. Three major fragmentation pathways were identified for the protonated molecules: formation of (a) benzoylium or (b) nitrilium ions through elimination of 71 and 72 u from the protonated molecules, respectively, and (c) elimination of 54 u from [M+H](+). These pathways were exploited by the density functional theory calculations combined with QTAIM studies. ConclusionsOur results can help in identifying 2-arene-2-oxazoline derivatives using electrospray ionization tandem mass spectrometry (ESI-MS/MS), which can be applied for monitoring reactions through the identified diagnostic ions (product ions). Also, we can suggest that benzoylium and nitrilium ions emerge during fragmentation under CID conditions. (AU)

• FAPESP's process: 17/04819-5 - Computational chemistry in studies of the reactivity of oxazolines: combining theory and experiment
• Grantee: Letícia da Silva Borges
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• FAPESP's process: 09/51812-0 - Development of a platform for the study of in vitro and in vivo metabolism of natural products, a need for pre-clinical testing system
• Grantee: Norberto Peporine Lopes
• Support Opportunities: BIOTA-FAPESP Program - Thematic Grants
• FAPESP's process: 09/08281-3 - Gas-phase reactivity of quinonoid compounds lapachol derivatives by electrospray ionization: Synergism between computational and experimental methods
• Grantee: Ricardo Vessecchi Lourenço
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 14/50265-3 - Distribution and metabolism of natural and synthetic xenobiotics: from the comprehension of reactional process to tissue imaging generation
• Grantee: Norberto Peporine Lopes
• Support Opportunities: BIOTA-FAPESP Program - Thematic Grants
• FAPESP's process: 20/02207-5 - Inventorying secondary metabolism applying metabolomic strategies: contribution to the Brazilian biodiversity valuation
• Grantee: Norberto Peporine Lopes
• Support Opportunities: BIOTA-FAPESP Program - Thematic Grants
• FAPESP's process: 18/14150-8 - Selective aromatic functionalization: Methodological Studies and new applications in the synthesis of BIOATIVE compounds
• Grantee: Giuliano Cesar Clososki
• Support Opportunities: Regular Research Grants
• FAPESP's process: 14/23604-1 - Computational chemistry: a tool to studies of mass spectrometry, reactivity and fragmentation/reaction mechanisms of organic compounds
• Grantee: Ricardo Vessecchi Lourenço
• Support Opportunities: Regular Research Grants