The molecular ion peak for alkyl halides ranges from observable for alkyl iodides to barely detectable for alkyl fluorides. Because of the isotope ratios for chlorine and bromine, the M+ and M+2 peaks are quite clear and indicate the presence of these elements.
The most important fragmentation process for alkyl halides involves simply losing the halogen to form an alkyl radical cation. For this reason, the mass spectra for halogenated compounds will often mimic those of simple alkanes.
For the lighter halogens (fluorine and chlorine) the loss of hydrogen halide is most important.
The complete mass spectrum for 1-bromohexane is given in figure 57, which illustrates these points.
Figure 56. Mass spectrum for 1-bromohexane.
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