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1981 (1)
1980 (1)
1Author    Gernot Frenking, Jochen Schmidt, Helmut SchwarzRequires cookie*
 Title    MNDO-Rechnungen zur unimolekularen CO-Abspaltung aus Isomeren C3H5CO + -Ionen MNDO Calculations on the Unimolecular CO Loss from Isomerie C3HsC0 + Ions  
 Abstract    In agreement with experimental results MNDO calculations indicate that unimolecular CO loss from the isomeric ions CH2 = CHCH2-CO+ (1), C-C3H5-CO+ (2), and CHsCH = CH-CO + (3), gives exclusively allyl cation (4). It is shown that, whereas CO loss from 1 is a continuously endothermic process, the analogous reaction from 2 and 3 follows relatively complicated pathways. For 2, the energetically most feasible reaction involves an isomerization of 2 to 1 via the intermediate a-oxo-and /?-oxocyclobutyl cations (8) and (9). This reaction sequence is 10 kcal • mol -1 lower in energy than direct CO loss from 2 coupled with isomerization of the incipient cyclopropyl cation (7) to allyl cation (4). For 3 it is shown that this ion undergoes isomerization to 2 prior to CO loss. The alternative reaction, i.e. direct CO elimination giving rise to 1-propenyl cation (11) or isomerization to 1 were 35 and 43 kcal • mol -1 higher in energy than the process 3 -* • 2. 
  Reference    Z. Naturforsch. 35b, 1031—1034 (1980); eingegangen am 21. März 1980 
  Published    1980 
  Keywords    Carbocation Chemistry, Quantum Mechanical Calculations, Potential Energy Surfaces 
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 TEI-XML for    default:Reihe_B/35/ZNB-1980-35b-1031.pdf 
 Identifier    ZNB-1980-35b-1031 
 Volume    35 
2Author    Gernot Frenking, Helmut SchwarzRequires cookie*
 Title    Frontorbitale und 1.2-Hydridwanderungen in Carbeniumionen Frontier Orbitals and 1,2-Hydrogen Shifts in Carbenium Ions  
 Abstract    For various carbenium ions it is shown that the energy value and the degree of localiza-tion of the LUMO have a significant influence on the energy barriers of 1,2-hydrogen shifts. The structures of the transition states are in line with the Hammond-Postulate. 
  Reference    Z. Naturforsch. 36b, 797—801 (1981); eingegangen am 10. März 1981 
  Published    1981 
  Keywords    Carbocation Chemistry, 1, 2-Hydrogen Migration, Frontier Orbitals, Quantum Mechanical Calculations, Transition States 
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 TEI-XML for    default:Reihe_B/36/ZNB-1981-36b-0797.pdf 
 Identifier    ZNB-1981-36b-0797 
 Volume    36