Go toArchive
Browse byFacets
Bookbag ( 0 )
'Hydrocarbons' in keywords Facet   section ZfN Section B  [X]
Results  3 Items
Sorted by   
Publication Year
1979 (1)
1978 (1)
1976 (1)
1Author    C. Wesdemiotis, H. Schwarz, C. C. Van De Sande, F. Van GaeverRequires cookie*
 Title    Transalkylierung und protonenkatalysierte C-C-Spaltung bei n-Butyl-und irc-Pentylbenzol in der Gasphase Transalkylation and Proton Catalyzed C-C-Cleavage of Gaseous n-Butyl and w-Pentyl Benzenes  
 Abstract    The investigation of several 13 carbon and deuterium labelled n-butyl and n-pentyl benzenes demonstrate that chemical ionization (reagent gas: methane) induces specific carbon-carbon bond cleavages of the alkyl group. The extent of competing reaction channels as for instance direct alkene elimination versus dealkylation/reprotonation is analyzed. Partial hydrogen exchange processes between reagent ions and substrate molecules are restricted to the phenyl ring. Intramolecular exchange reactions between the side chain and the aromatic ring which are typical for the open shell molecular ions of alkyl benzenes are not observed for analogous closed shell cations. Die von Munson und Field [1] in die Massen-spektrometrie eingeführte Methode der Chemischen Ionisation (CI) hat sich nach einer längeren Induk-tionsperiode innerhalb weniger Jahre als ein wir-kungsvolles Instrument bei der Lösung vielfältigster Problemstellungen in der Chemie erwiesen [2]. Bei diesem Verfahren werden durch Elektronenstoß-ionisation (EI) aus einem gegebenen Reaktandgas diverse Ionen erzeugt, die dann ihrerseits mit Sub-stratmolekülen M z.B. im Sinne von Säure/Base-Reaktionen reagieren. Verwendet man beispiels-weise Methan als Reaktandgas, so liegen als reaktive Species hauptsächlich [CHs] + , [C2Hö] + und [C3H5] + vor; diese ionisieren die Substratmoleküle M in schnellen Ion/Molekülreaktionen [3], wobei u.a. Ionen vom Typ [MX]+ entstehen (X = H, C2H5, C3H5). Die reaktiven Eigenschaften solcher "closed 
  Reference    Z. Naturforsch. 34b, 495—501 (1979); eingegangen am 8. Dezember 1978 
  Published    1979 
  Keywords    Chemical Ionization, Carbocations, Hydrocarbons 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_B/34/ZNB-1979-34b-0495.pdf 
 Identifier    ZNB-1979-34b-0495 
 Volume    34 
2Author    J. Heimbrecht, K. Levsen, H. SchwarzRequires cookie*
 Title    and their [M-CH3] + Fragments  
 Abstract    In contrast to the corresponding butyl ions the [M-CH3]+ ions from isomeric pentyl-benzenes do not isomerise completely to a mixture of interconverting structures prior to decomposition. 
  Reference    (Z. Naturforsch. 31b, 1299—1300 [1976]; received June 3 1976) 
  Published    1976 
  Keywords    Collisional Activation Spectra, Isomerisation, Mass Spectra, Hydrocarbons 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_B/31/ZNB-1976-31b-1299_n.pdf 
 Identifier    ZNB-1976-31b-1299_n 
 Volume    31 
3Author    Chrysostomos Wesdemiotis, Helmut Schwarz, Friedrich Borchers, Heinz Heimbach, Karsten LevsenRequires cookie*
 Title    Massenspektrometrische Untersuchungen zur Genese von [M—Me] [M-Et] [C7H7]+ und [C7H8]+ aus n-Butyl-und n-Pentylbenzol: Zeitabhängige Nachbargruppeneffekte, Isomerisierungen und kompetitive Wasserstoff-Umlagerungen Mass Spectrometric Investigations on the Formation of [M-Me]+, [M-Et]+, [C7H7] + and [C7H8] + - from w-Butyl and w-Pentyl Benzenes: Time Dependent Neighbouring Group Participation, Isomerization and Competitive Hydrogen Rearrangements  
 Abstract    The details of the elimination of CH3 1 and C2Hs -from the molecular ions of n-butyl and n-pentyl benzenes as well as the formation of C7H7+ and C7Hs + -have been established using a combination of different mass spectrometric techniques. Among these techniques are field ionization kinetics (FIK), collisional activation (CA), unimolecular decomposi-tion of metastable ions (MI), kinetic energy release determinations (Tkin)> appearance potential measurements (AP) as well as high resolution mass spectrometry. The appli-cation of these methods and the investigation of nine 13 carbon and eleven deuterium labelled n-butyl and n-pentyl benzenes clearly demonstrate that 1) the loss of methyl and ethyl from terminal positions of the alkyl chains are accompanied by an interaction with the phenyl ring and 2) the regioselectivity of these processes is time dependent. Contrary to previous conclusions it is shown that hydrogen transfer in the formation of C7H8 + -occurs via five-, six-and seven-membered transition states. The time dependence of the hydrogen exchange reaction preceding the alkene eliminations is discussed in detail. 
  Reference    Z. Naturforsch. 33b, 1150—1164 (1978); eingegangen am 1. März 1978 
  Published    1978 
  Keywords    Hydrocarbons, Hydrogen Rearrangement, Metastable Ions, Collisional Activation, Field Ionization Kinetics 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-1150.pdf 
 Identifier    ZNB-1978-33b-1150 
 Volume    33