A hidden hydrogen transfer in the unimolecular reaction of 1,2-dimethoxyethane(center dot+)

The metastable dimethoxyethane radical cation 1 eliminates methanal to give the CH3O+(H)(CH2CH2)-H-. distonic ion 2 (m/z 60, 80%) and methanol to yiel d the C3H6O.+ (m/z 58, 20%) fragment. The first process is well-known, begi nning with the transfer of a hydrogen from a methoxy group to the oxygen of the other to yield the intermediate distonic ion . CH2OCH2CH2O+(H)CH3, 3. It is shown, from FTICR experiments, that the m/z 58 fragment possesses the CH3OCHCH2.+ structure 5. From energetic studies, it can be established tha t both fragmentations involve the same intermediate 3. The existence of a h idden 1,4-H transfer from carbon to carbon in the formation of 5 is shown. The energy profile is elucidated by the behavior of metastably decomposing stable isotopically labeled 1,2-dimethoxyethane radical cation 1.