Fragmentation patterns in mass spectrometry

This bond breaking does not occur randomly it tends to form the most stable fragments. By knowing what stable fragments result from different kinds of compounds, we can recognize structural features and use the mass spectrum to confirm a proposed structure. 

A similar fragmentation gives an ethyl cation and a butyl radical. In this case, the ethyl fragment m/z 29) is detected. 

Symmetric cleavage of hexane gives a propyl cation and a propyl radical. 

Most molecular ions have even mass numbers. Most fragments have odd mass numbers. (With a nitrogen atom, the molecular ion is odd and most fragments containing N are even.) 

Cleavage to give a pentyl cation m/z 71) and a methyl radical is weak because the methyl radical is less stable than a substituted radical. Cleavage to give a methyl cation m/z 15) and a pentyl radical is not visible because the methyl cation is less stable than a substituted cation. The stability of the cation is apparently more important than the stability of the radical, since a weak peak appears corresponding to loss of a methyl radical, but we see no cleavage to give a methyl cation. 

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Fragmentation Patterns in Mass Spectrometry 548 Summary Common Fragmentation Patterns 553 EssentialTerms 555 Study Problems 556... 

Generally, the structure of fatty compounds offers two possibilities for performing derivatization reactions with the objective of improved fragmentation patterns in mass spectrometry. The first possibility is derivatization at the carboxylic acid moiety (C-1 remote-site derivatization ) the second possibility is derivatization of functional groups in the main fatty acid chain. Often both kinds of derivatization are carried out on one sample to facilitate analysis. 

Fragmentation pattern In mass spectrometry, the ions produced by dissociation of the molecular ion. 

In response to reviewer feedback, new sections have been added on fragmentation patterns in mass spectrometry (Section 13.3) and peptide sequencing (Section 28.6). In addition, sections on splitting in NMR spectroscopy (Section 14.7) and substituent effects in substituted benzenes (Section 18.6) have been rewritten to clarify and focus the material. Some mechanisms have been modified by adding electron pairs to nucleophiles and leaving groups to more clearly indicate the course of the chemical reaction. 

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