Studies of cyclic acetals. XXII—limitations on the use of alkyl substituents as pseudoisotopic labels: The electron impact mass spectra of alkylated derivatives of 3,7,9- and 4,7,9-trioxabicyclo[4·2·1]nonanes

Low resolution, electron impact mass spectra are tabulated for eleven methylated derivatives of 3,7,9-trioxabicyclo[4·2·1]nonane, 4,7,9-trioxabicyclo[4·2·1]nonane and nine methylated derivatives, and 6-ethyl-3,7,9-trioxabicyclo[4·2·1]nonane. In general, a substantial proportion of the fragmentation subsequent to electron impact can be rationalized according to a few, simple decomposition pathways that are inferred from analysis of mass number shifts caused by changes in substitution; however, major alterations in fragmentation are apparent in a few of these examples, which signals that, for several of the 4,7,9-trioxabicyclo[4·2·1]nonanes, the substituent acts not as an inert label but as a fragmentation-directing group.