FRAGMENTATION OF COLLISIONALLY ACTIVATED 2-METHYL-3-HYDROXYPHENOXIDE,4-METHYL-3-HYDROXYPHENOXIDE AND 5-METHYL-3-HYDROXYPHENOXIDE ANIONS INTHE GAS-PHASE

Low-energy collisionally activated dissociation (CAD) of O-deprotonate d 2-, 4- and 5-methylresorcinol in the gas phase largely causes fragme ntation to form ions analogous to those observed in the CAD spectrum o f resorcinol. The anions of the three isomers decompose in processes i nitiated by the migration of the remaining oxygen-bound hydrogen atom to the adjacent ring carbons. 5-Methylresorcinol also decomposes by th e expulsion of the elements of ketene. The mechanisms of these fragmen tation processes were studied by the use of both NH3 and D2O as deprot onation agents, deuterium labeling of ring carbon atoms and the study of the decomposition pattern of 4,6-dimethyl-2-pyrone.