| Abstract: | Bromine, fluorine and/or chlorine atoms on one cyclopropyl ring jointly influence the dominant primary modes of electron-impact induced fragmentation. Decomposition ions include CBrX, C2HQ2X and C3HQ2X2, where × is an halogen atom and Q is from the group of an halogen atom, an hydrogen atom and a methyl group. For none of the compounds studied was formation of an ionic CBrX the dominant primary process. Gem-dibromo-gem-dihalocyclopropanes preferentially eliminated dibromo divalent carbon and formed decomposition products of gem-dihalogenated C2HQ2X′s. In cases where more stable allyl ions were formed, fragmentation was through C3HQ2X2. Upon electron-impact, the ions CF, CHF2 and CF3 were produced in abundances directly related to the fluorine content of their cyclopropyl precursors. When fragmentation patterns for internally generated radical ions of the composition C2HQ2X were compared with patterns obtained by direct introduction of the same fluoroolefins into a mass spectrometer, incomplete correspondence was found. Variation in the mode of decomposition can be a consequence of differences in the energy levels of the olefin fragmented. Addition of two hydrogen atoms from water to quinones and to s-tetrazines is well established in the literature. Reaction of an additional cyclic series, polyhalocyclopropanes, with water prior to electron-impact is suggested. |
