During the last two decades there has been considerable growth in the development of electrospray ionization mass spectrometry (ESI-MS) as a practical method in the study of reaction mechanisms. This method allows the interception and characterization of key intermediates, either as transient species or as protonated/deprotonated forms of neutral species by API-MS. The outstanding features and advantages of ESI-MS make it one of the most suitable tools for the fast screening of intermediates...