- Intermediacy of ion neutral complexes in the fragmentation of short-chain dialkyl sulfides
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The main fragmentation processes after electron ionization of butyl methyl and butyl ethyl sulfides are rationalized by the intermediacy of the ion neutral complex [RSH · methylcyclopropane](+·) as demonstrated by extensive labeling and collision activation studies.
- Filsak,Budzikiewicz
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p. 601 - 610
(2007/10/03)
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- A McLafferty Rearrangement in an Even-electron System: C3H6 Elimination from the α-Cleavage Product of Tri-n-butylamine
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It is shown by deuterium labelling, linked-scan measurements and collision activation that the .>+ (α-cleavage) ion in the electron impact ionization spectrum of tributylamine loses C3H6 with transfer of one hydrogen specifically from the γ-position.The experimental data point towards a mechanism which involves the intermediate formation of a distonic diradical ion from an excited α-cleavage ion which the eliminates the neutral alkene.
- Budzikiewicz, Herbert,Bold, Peter
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p. 709 - 712
(2007/10/02)
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- Pseudo One-Step Cleavage of C-C Bonds in the Decomposition of Ionized Carboxyclic Acids. Radical Like Reactions in Mass Spectrometry
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Metastable molecular ions of hexanoic acid (1) decompose unimolecularly to C2H5. and protonated methacrylic acid (5-H+)(92percent rel. abund.).Investigation of the mechanism reveals that 1) the branched cation radical 11 must be regarded as the essential intermediate in the course of the rearrangement/dissociation reaction and 2) the process commences with intramolecular hydrogen transfer from either C-3 or C-5 to the ionized carbonyl oxygen ("hidden" hydrogen migration).Hydrogen transfer from C-4, which would correspond to the well-known McLafferty rearrangement, is of no importance in the C2H5.-elimination from 1.The same conclusion applies for various alternative mechanisms, as for example a SRi type reaction, 1 -> 2-H+.The gas phase chemistry of the cation radical of 1, and in particular the hydrogen exchange processes between the methylene groups C-2/C-3 and C-5/C-6, is in surprisingly close correspondence to the chemistry of free alkyl radicals. - The syntheses of various 13C and 2H-labelled model compounds are described.
- Weiske, Thomas,Schwarz, Helmut
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p. 323 - 347
(2007/10/02)
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