Pyranones, radicals from

The RDA cleavage of (129) consists of expulsion of neutral methylacetylene with the formation of the acetylketene radical cation at m/e 84 loss of a methyl radical gives the abundant ketene ion (18b). The isomeric pyran-4-one (130) fragments similarly. In this case, however, RDA cleavage of the pyranone ring is followed by loss of CO, producing methylketene ions, m/e 56. Carbon monoxide loss from the molecular ion also occurs but to a lesser extent than for (129). 

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