Zum Mechanismus massenspektrometrischer Fragmentierungsreaktionen–II: Methoxygruppenwanderungen und Ringfragmentierungen in den Massenspektren der Methylather cyclischer Polyalkohole

The mass spectra of methyl ethers of cyclopentane-, cyclohexane- and cycloheptanediols contain a characteristic m/e 75 peak of ions of the structure ⊕CH(OCH₃)₂, which are formed by 1,3-, 1,4- or 1,5-migration of a methoxy group. The formation of these ions does not depend on the stereochemistry of the original molecule; probably the methoxy group migration occurs after α-cleavage of the molecular ion in an open chain radical ion: In the case of cycloalkanes with three or more methoxy groups the m/e 75 rearrangement ions give rise to one of the most prominent peaks of the mass spectra. Chemical bonds, terminating at a carbinol-C-atom, are weaker than normal. The presence of several carbinol-C-atoms in the molecular ions of cyclic polymethoxy compounds therefore favours fragmentations which differ from those of simple derivatives of cyclanols and which are typical of the position of the methoxy groups.