- Ion-Neutral Complexes as Intermediates in the Decompositions of C5H10O2.+ Isomers
-
Ionized pentanoic acid, 3-methylbutanoic acid, and the enol isomer of ionized isopropyl acetate are shown to pass in part through common intermediates before decomposing to CH3C.HC(OH)2+ (7) and the "McLafferty + 1" ion CH3C(OH)2+ (10).The H transfer to form the methyl of CH3C(OH)2+ and the joining of two CH2 groups to form the C-C bond in the ethylene eliminated to produce CH3C.HC(OH)2+ are both attributed to reactions of the ion-neutral complex .H2C(OH)2+>.The McLafferty + 1 ion is also formed, especially from ionized esters, by another pathway in which complexes may or may not be intermediates.The intermediacy of the ion-neutral complexes is supported by energetic considerations, isotope effects, and the decomposition patterns of labeled ions.The latter correlate with a preference for hydrogen transfer from the end carbons of the C3 partner in other reactions proposed to be complex-mediated.Unification of the McLafferty rearrangement, the McLafferty + 1 rearrangement, and the McLafferty rearrangement with charge reversal by a common initial γ-hydrogen rearrangement followed by dissociation or isomerization in ion-neutral complexes is proposed.Group migration by 1,2-shifts, possibly by dissociation to form a double bond in one partner in an ion-neutral complex followed by addition at the opposite end of the double bond, is shown to be a general reaction of ions in the gas phase.
- McAdoo, David J.,Hudson, Charles E.,Skyiepal, Mark,Broido, Ellen,Griffin, Lawrence L.
-
p. 7648 - 7653
(2007/10/02)
-
- Unimolecular Dissociations of the +. Metastable Ion
-
The metastable molecular ion of 2-hexanone loses a methyl radical mainly (ca. 80percent) from positions C(4) and C(6), in equal proportions, as indicated by 13C labelling.The necessary skeletal rearrangement of the butyl chain is interpreted in terms of a 1,2-+. shift .The results and the mechanisms concerning the minor eliminations of C2H4, C2H5., C3H5. and C3H6 neutrals are also discussed.
- Bouchoux, Guy,Tortajada, Jeanine,Dagaut, Jacques,Fillaux, Joelle
-
p. 451 - 457
(2007/10/02)
-