38. “The loss of a methyl radical and the retro diels - Alder reaction in the electron impact mass spectrometry of 2-cyclohexen-1-ol and related compounds”
    Braem, D.; Gülaçar, F. O.; Burger, U.; Buchs, A.
    Org. Mass Spectrom. 1979, 14, 609-617.

The electron impact mass spectra of 2-cyclohexen-1-ol and of several of its ²H and ¹³C labelled analogues show that the molecular ions lose a methyl radical by a completely different means from the mechanism described previously. Moreover, the retro Diels–Alder reaction also proceeds in a non-classical way; in addition to the elimination of an olefinic molecule from unrearranged molecular ions, a second more important route implies a formal 1,3 allylic rearrangement prior to the retro Diels–Alder reaction. The mass spectra of a series of alkyl substituted homologues show that the competition between the two processes is closely related to the size of the olefinic moiety that is expelled.

DOI : 10.1002/oms.1210141108