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  • Tandem mass spectrometry  (9)
  • Neutralization-reionization mass spectrometry  (8)
  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 983-987 
    ISSN: 1434-1948
    Keywords: Telluroles ; Neutralization-reionization mass spectrometry ; DFT calculations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2,2-Dichloro-1,3-dichalcogena-2-telluroles of sulfur and selenium, C6H4[XTe(Cl)2Y] with X, Y = S, Se, serve as precursors to generate the cation radicals of 1,3-dichalcogena-2-telluroles C6H4[XTeY]+• as well as the corresponding neutral counterparts by means of neutralization-reionization mass spectrometry. These neutral 2-telluroles are intrinsically stable for at least 1 μs in the gas phase. The most abundant fragmentation channel at the neutral and cationic stages is due to loss of atomic tellurium to afford the corresponding benzo-1,2-dichalcogena-cyclobutenes. For the latter, partial isomerization to the related dichalcogena-ortho-quinones is indicated by the mass-spectrometric fragmentation pattern.
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  • 2
    ISSN: 1434-193X
    Keywords: Neutralization-reionization mass spectrometry ; Density functional theory ; Oxyallyl ; Ketocarbenes ; Methoxy vinylidene ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Five different anionic [C3, H4, O]·- isomers, i.e. the radical anions of acrolein, acetyl carbene, formyl methyl carbene, methoxy vinylidene, and oxyallyl are generated in an ion beam mass spectrometer and subjected to neutralization-reionization (NR) mass spectrometric experiments including neutral and ion decomposition difference (NIDD) mass spectrometry; the latter allows for the examination of the neutrals′ unimolecular reactivity. Further, the anionic, the singlet and triplet neutral, and the cationic [C3, H4, O]·-/0/·+ potential-energy surfaces are calculated at the B3LYP-6-311++G(d, p) level of theory. For some species, notably the singlet state of oxyallyl, the theoretical treatment is complemented by G2, CASSCF, and MR-CI calculations. Theory and experiment are in good agreement in that at the neutral stage (i) acrolein does not react within the μsec timescale, (ii) acetyl and formyl methyl carbenes isomerize to methyl ketene, (iii) methoxy vinylidene rearranges to methoxy acetylene, (iv) singlet 1A1 oxyallyl undergoes ring closure to cyclopropanone, and (v) triplet 3B2 oxyallyl may have a lifetime sufficient to survive a NR experiment.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 141-147 
    ISSN: 0009-2940
    Keywords: Bond activation, C  -  H, C  -  C ; Transition-metal ions ; Neighbouring group participation ; Tandem mass spectrometry ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The metastable-ion mass spectra of Fe+ complexes of alkanedinitriles NC(CH2)nCN (n = 1 - 10) exhibit six types of reactions: (1) Loss of the intact ligand to regenerate bare Fe+ as the exclusive (n = 1) or major reaction (n = 2) for the lower homologues; (2) generation of nitriles H(CH2)mCN with m = 0 - 6; (3) formation of unsaturated nitriles CH2 = CH(CH2)mCN with m = 0 - 4; (4) production of C2H4; (5) dehydrogenation, and (6) expulsion of the radicals C2H5 and CH2CN+. The branching ratios of these competing processes are governed by the chain length (CH2)n separating the two CN groups. Mechanistic insight is provided by the study of isotopomers. A comparison of the present data with the previously described behaviour of RCN/Fe+ complexes (R = alkyl) leaves no doubt that for the α,ω-alkanedinitriles it is the Fe+-mediated interaction of the two functional groups which controls the gas-phase chemistry of these organometallic systems. For example, results are presented demonstrating inter alia that losses of H2 and C2H4 proceed by completely different pathways when dinitriles serve as precursors, and either reaction is affected by neighbouring group participation. In distinct contrast, for RCN/Fe+ complexes (R = alkyl) the existing data point to common intermediates.
    Additional Material: 4 Tab.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 1583-1586 
    ISSN: 0009-2940
    Keywords: Transition-metal ions ; Bond activation, CH and CC ; Olefine activation ; Tandem mass spectrometry ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mechanistic details (i.e. β-versus γ-hydrogen transfer) of transition-metal ion induced generation of propene from metastable ion complexes of 1,7-octadiene with M+=Cr+, Fe+, Ni+ are strongly affected by the nature of M+. For Cr+ the major reaction involves the transfer of an allylically activated hydrogen atom to M+ (γ-H transfer), followed by coupling of this hydrogen with the C3H5 unit (Scheme 3: 8 → 9→ 11 → C3H6). The hydrogen transfer 9→ 11 is preceded by substantial exchange reactions. A minor path for M+=Cr+ corresponds to the more traditional β-hydrogen transfer 9→ 10. This process, however, represents the major route for propene loss induced by M+ = Fe+, Ni+.
    Additional Material: 1 Tab.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 2069-2071 
    ISSN: 0009-2940
    Keywords: Interstellar chemistry ; Polycarbon disulfides ; Neutralization-reionization mass spectrometry ; Beam experiments ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title compounds are generated and characterized in the gas phase by tandem mass spectrometry (neutralization-reionization mass spectrometry); it is demonstrated that both even and odd-numbered polycarbon disulfides S(Cn)S(n = 2-6) are stable species. The elusiveness of the even-numbered analogues (n = 2, 4, 6) in the condensed phase must be due to facile intermolecular reactions.
    Additional Material: 2 Tab.
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  • 6
    ISSN: 0009-2940
    Keywords: Charge-transfer experiments ; Tandem mass spectrometry ; Diazene ; Potential energy surface ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Collision experiments demonstrate that isodiazene (H2NN) and its radical cation are viable molecules in the gas phase. The mass-spectrometric experiments are complemented by extensive ab-initio MO calculations using the GAUSSIAN-2 procedure in order to map out relevant parts of the potential energy surface of H2N2 (singlet) and H2N2+· (doublet).
    Additional Material: 6 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1171-1173 
    ISSN: 0009-2940
    Keywords: Tandem mass spectrometry ; Collision experiments ; Sulfur-nitrogen clusters ; Electron transfer ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Collision experiments on NS-x (x = 2, 3) clusters are reported. Evidence is presented for the gas-phase existence of the corresponding NS.x and NS+x species. For x = 3, the mass spectra are very much in keeping with a connectivity SS-NS (5) for all three charge states. For x = 2, the experimental data favor the presence of NSS (2); however, the cyclic C2v-symmetric form 3 cannot be ruled out.
    Additional Material: 4 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 1803-1805 
    ISSN: 0009-2940
    Keywords: Beam experiments ; Interstellar chemistry ; Dicarbon sulfide ; Butatrienedithione ; Neutralization-reionization mass spectrometry ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title compounds are generated and characterized in the gas phase by mass spectrometric methods (neutralization-reionization mass spectrometry), and for dicarbon sulfide the experimental results are supported by ab initio MO calculations (HF/6-31G*).
    Additional Material: 4 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 261-265 
    ISSN: 0009-2940
    Keywords: Bond activation ; C—H ; C—C ; Iron chemistry ; Reaction mechanisms ; Chelate effects ; Tandem mass spectrometry ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: For three α,ω-diphenylalkanes the mechanistic details of the Fe+-mediated activation of C—H and C—C bonds in the gas phase have been elucidated by isotopic labelling experiments. The unimolecular reactions, i.e. dehydrogenation of the alkane chain, formation of ethylene from internal methylene groups, and generation of toluene, proceed largely with high selectivity. Particularly interesting are the results for the dehydrogenation of the Fe+ complex 3-Fe+ of 1,8-diphenyloctane which involves to 93% the internal methylene groups C-4/C-5. In addition, the study of the stereoisotopomers 3c-d provides evidence for the operation of isotopically sensitive branching (“metabolic switching”) in the reaction, and the analysis of the data suggests that the selectivity of the reaction is, most likely, due to a sandwich-type structure.
    Additional Material: 3 Tab.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 1679-1680 
    ISSN: 0009-2940
    Keywords: Bond activation, C — H, C — C ; Transition-metal ions ; Tandem mass spectrometry ; Geminal dialkyl effect ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Depending on the internal energy content, due to the operation of a geminal dialkyl effect, the Fe+ -mediated dehydrogenation of α,α-dimethyl-substituted ketones preferably involves the more substituted alkyl chain.
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