investigation of the structures of isomeric ions derived from acetone, diacetone alcohol, and mesityl oxide. Can. J. Chem. 66, 591 (1988). An investigation of the structures of isomeric ions formed in ion/molecule reactions occurring in 2-propanone (acetone), 4-hydroxy-4-methyl-2-pentanone (diacetone alcohol), and 4-methyl-3-penten-2-one (mesityl oxide) has been performed using a hybrid mass spectrometer of reversed geometry. Ions of mlz 1 17, which have been observed as products of ion/molecule reactions in acetone and in diacetone alcohol, may have a single structure if an aldol type condensation reaction occurs under acidic conditions in the gas phase; however, high energy collision induced dissociation (CID) results proved the two ions to be isomeric only.Dehydration of the mlz 1 17 ions produced a species of mlz 99 which, in the case of diacetone alcohol, may have the structure of protonated mesityl oxide. That the mlz 99 ion formed was unique to each system was demonstrated by high energy CID and kinetic energy release (KER) spectrometry. In the acetone system, CID results suggested that rnlz 99 was an ion-dipole complex of c~H:(cH~)~co; this hypothesis was tested by clustering C~H: with (CD3)?C0 and comparison of its CID results with those obtained above. In the case of mlz 99 derived from diacetone alcohol or mesityl oxide, the neutral lost via metastable decomposition in the second field-free region was found to be C4Hs, presumably 2-methyl propene. While the ion of mlz 99 may also eliminate methane to yield a species of mlz 83, the dominant metastable elimination from this ion is carbon monoxide rather than ethene as shown by collision induced dissociative ionization (CIDI). The ions of mlz 83 observed in the two systems exhibit very similar CID spectra; however, a small variation in the yield of products of mlz 41 and 43 suggests two structures for the ion derived from diacetone alcohol, one of which is identical to that seen in mesityl oxide.
RAYMOND EVANS MARCH et ALEXANDER BALDWIN YOUNG. An investigation of the structures of isomeric ions derived fromacetone, diacetone alcohol, and mesityl oxide. Can. J. Chem. 66, 591 (1988). Utilisant un spectromktre de masse de gComCtrie inversee, on a Ctudie les structures des ions isomkres qui se foment au cours des rkactions molCculaires se produisant dans la propanone-2 (acktone), I'hydroxy-4 methyl-4 pentanone-2 (diacktone alcool) et la mCthyl-4 pentkne-3 one-2 (oxyde de mksityle). I1 est possible que les ions de mlz 117, qui sont observCs comme produits dans les rkactions ionlmolCcules de I'acCtone et du diacCtone alcool, aient une structure unique si une reaction de type aldolique se produit dans des conditions acides, en phase gazeuse; toutefois, il est possible que des resultats de dissociations induites par des collisions B hautes Cnergies (DIC) prouvent que les produits ne sont que des isomkres.La deshydratation des ions de mlz 1 17 fournit une espkce de mlz 99 qui, dans le cas du diacCtone alcool, pourrait correspondre B un oxyde de mCsityle protonC. ...