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)