Pyrolysis Process Compared to Ion Fragmentation in Mass Spectrometry

6 Pyrolysis Process Compared to Ion Fragmentation in Mass Spectrometry. 

In mass spectrometry, the electrons interact with the molecules M to eject an additional electron leaving a positively charged species (with an odd number of electrons) of the type M The ions also receive energy during the electron impact, and the excess of energy induces fragmentation (with fragment ions A commonly but not always with an even number of electrons)  

The formation of molecular ions takes place with a range of internal energies, and more than one fragmentation path is possible for a given molecule. The mass spectrum is given as a chart showing the ion abundance (normalized to the most abundant ion) versus m/z of the fragments. For the interpretation of the mass spectra, two main questions should be answered, namely  

The presence of heteroatoms with non-bonding n electrons favors the localization of charges. When the radical and/or the charge are localized, this influences the fragmentation and the reaction mechanisms can be classified as sigma electron ionizations, localized charge initiations, radical site initiations, and rearrangements. 

If the radical is formed by the loss of an electron from a given a bond, such as a bond to a highly substituted carbon, the cleavage at this location will be favored sigma electron ionization mechanism). 

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