Free Radicals in Mass Spectrometry. Part I. General Fragmentation Rules for Organic and Organometallic Compounds under Electron Impact

Abstract

General fragmentation rules for isomerization and fragmentation processes based on firm thermochemical grounds are presented for positive odd- and even-electron ions. The thermochemical approach by ions' and free radicals' heats of formation, appearance and critical energies allowed the unification of many known fragmentation and isomerization processes. It is shown that to describe more than 180 classes of organic and hetero-organic compounds it is sufficient to apply only 21 types of isomerization and fragmentation processes. Most of these types are characterized with a specific mechanism and the stabilization morde for ions and/or neutral species. Many original fragmentation schemes are given. In addition to simple bond cleavages, it was demonstrated that the quasi-equilibrium theory of Eyring et al. Is applicable to each step of the multi-stage rearrangement rather than to the summary rearrangement process.