The mass spectra of cycloalkenes show distinct molecular ion peaks. It may be impossible to locate the position of a double bond due to migration. The mechanism of fragmentation for cyclic alkenes is virtually the same as for straight chain alkenes. One noteworthy characteristic is the fragmentation of cyclohexenes which undergo a reverse Diels-Alder reaction as indicated in Figure 16. The complete mass spectrum for cyclohexene is given in Figure 17.
Figure 16. Mechanism of fragmentation for cyclohexene.
Figure 17. Mass spectrum for cyclohexene.
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