Online Mechanistic Investigations of Catalyzed Reactions by Electrospray Ionization Mass Spectrometry: A Tool to Intercept Transient Species in Solution

During the last two decades there has been considerable growth in the development of electrospray ionization mass spectrometry (ESI-MS) as a practical method for studying reaction mechanisms. This tool allows interception and characterization of several key intermediates, either as transient species or as protonated/deprotonated forms of neutral species. Reaction pathways shown by ESI-MS(/MS) have been probed by gas-phase ion/molecule reactions, and expanded mechanisms have been elaborated based on mass spectrometric data. The successful application of ESI-MS in revealing, elucidating, and helping to consolidate proposed mechanisms of organic reactions is emphasized. This is meant to serve as a foundation for future investigations in this rapidly developing area of research. Outstanding features and advantages of ESI-MS make it one of the most suitable tools for the fast screening of intermediates directly from solution; it has significantly increased the chemical information available to organic chemists. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)