Abstract
Protonation of organic compounds and fragmentations of resulting protonated molecules are reviewed. In chemical ionization (CI) mass spectrometry, the amount of protonation and the extent of bond cleavages of typical functional groups are evaluated by using appropriate test compounds. A new parameter, protonation susceptibility (PS), is introduced, which is not directly related to the ordinary proton affinity (PA) of organic compounds. CI mass spectra of a series of compounds are quantitatively analyzed, and prediction of an unknown spectrum is shown to be successful. The principal modes of bond cleavages in even-electron ions are also formulated. These results are compared to the protonation in fast atom bombardment (FAB) and electrospray ionization (ESI) mass spectra, where the protonation takes place in condensed phase-like environment and in solution, respectively.
