Investigations of the fragmentation pathways of benzylpyridinium ions under ESI/MS conditions

• Published in: Journal of mass spectrometry. Vol. 44; no. 12; pp. 1668 - 1675
• Main Authors: Zins, Emilie-Laure, Rondeau, David, Karoyan, Philippe, Fosse, Céline, Rochut, Sophie, Pepe, Claude
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01-12-2009; Wiley; Wiley-Blackwell
• Subjects: benzylpyridinium ions; Bombardment; Chemical Sciences; Chemistry; DFT calculations; Exact sciences and technology; Fragmentation; Internal energy; ion/molecule reactions; Ionization; Mass spectrometers; Mass spectrometry; Mathematical analysis; Organic chemistry; Pathways; Reactivity and mechanisms; tropylium ions; Substituent effect; Ion molecule reaction; Tandem mass spectrometry; Collisional activation; Organic cation; Theoretical study; Fragmentation pattern; Experimental study; Electrospray; DFT calculations; benzylpyridinium ions; Fast atom bombardment mass spectrometry; tropylium ions; Density functional method; ion/molecule reactions; mass spectrometry; Gas phase; MIKE mass spectrum
• ISSN: 1076-5174; 1096-9888; 1096-9888
• DOI: 10.1002/jms.1672

Benzylpyridinium ions are often used as 'thermometer ions' in order to evaluate the internal energy distribution of the ions formed in sources of mass spectrometers. However, the detailed fragmentation pathways of these parent ions were not well established. In particular, fragmentation involving a rearrangement (RR) process may be influencing the simulated distribution curves. In a previous study, we suggested that such RR actually occurred under electrospray ionization/mass spectrometry (ESI/MS) and fast atom bombardment/mass spectrometry (FAB/MS) experiments. Here, we present a systematic study of different substituted benzylpyridinium ions. Theoretical calculations showed that RR fragmentation leading to substituted tropylium ions could occur under 'soft ionization' conditions, such as ESI or FAB. Experimental results obtained under gas-phase reactivity conditions showed that some substituted benzylpiridinium compounds actually undergo RR fragmentations under ESI/MS conditions. Mass-analyzed kinetic experiments were also carried out to gain information on the reaction pathways that actually occur, and these experimental results are in agreement with the reaction pathways theoretically proposed. Copyright © 2009 John Wiley & Sons, Ltd.