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'Radical Cation' in keywords Facet   Publication Year 1982  [X]
Facet   section ZfN Section B  [X]
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1Author    Gemot Frenking, Helmut SchwarzRequires cookie*
 Title    ab i/ifüo-Rechnungen zur relativen Stabilität der Neutralmoleküle, Radikalkationen und -anionen von Allen und Propin ab initio Calculations on the Relative Stabilities of the Neutrals, Radical Cations and Anions of Allene and Propvne  
 Abstract    Ab initio calculations demonstrate that, in agreement with experimental results, the oxidation of both allene (1) and propyne (2) to their corresponding cation radicals (1+ -and 2+ -) is associated with a reversal of the stability order. Whereas for the neutral molecules 1 is thermochemically less stable than 2 (zMHf° = 1.3 kcal/mol) the opposite holds for the cation radicals (1+ -is 13.3 kcal/mol more stable than 2 +-). The radical anions of 1 and 2 do also show a reversed stability order (l +< being 5.1 kcal/mol more stable than 2 _ .); however, both radical anions are predicted to undergo spontaneous electron detachement, thus giving their neutral counterparts (negative electron affinities). The changes in geometries and charge distributions associated with the redox reactions of 1 and 2 are briefly dis-cussed. 
  Reference    Z. Naturforsch. 37b, 1602—1605 (1982); eingegangen am 5. August 1982 
  Published    1982 
  Keywords    Molecular Orbital Calculations, Unsaturated Hydrocarbons, Radical Cations, Radical Ions 
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 TEI-XML for    default:Reihe_B/37/ZNB-1982-37b-1602.pdf 
 Identifier    ZNB-1982-37b-1602 
 Volume    37 
2Author    Gemot Frenking, Nikolaus Heinrich, Jochen Schmidt, Helmut SchwarzRequires cookie*
 Title    Neutrale und ionische Keto/Enoltautomere: Zum Ursprung der Stabilitätsumkehr und zu ungewöhnlichen Substituenten-Effekten Neutral and Ionic Keto/Enol Tautomers: On the Origin of Stability Reversal and Unusual Substituent Effects  
 Abstract    The reversal in stability for neutral keto/enol tautomers and their cation radicals is mainly due to the removal of an electron from an ^-orbital of the enol, which has anti-bonding properties for the C-0-bond. The total electronic energy gained in the oxidation of enols is more than sufficient to compensate for the increase in nuclear/nuclear repulsion when comparing keto/enol tautomers; this, however, does not hold for the keto systems investigated. The marked methyl substituent effect found in O, C-l, and C-2 substituted enol cation radicals is not reflected in the charge distribution of the corresponding ions. Comparison of the MNDO calculated heats of formation of ions with that of their neutral counterparts indicates that the changes in bond dissociation energies account at least qualitatively for the experimentally observed effects. 
  Reference    Z. Naturforsch. 37b, 1597—1601 (1982); eingegangen am 30. Juni 1982 
  Published    1982 
  Keywords    Molecular Orbital Calculations, Methyl Substituent Effects, Gas Phase Ion Stability, Radical Cations, Radical Anions 
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 TEI-XML for    default:Reihe_B/37/ZNB-1982-37b-1597.pdf 
 Identifier    ZNB-1982-37b-1597 
 Volume    37