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Radical Cations of Phenyl-Substituted Aziridines: What Are the Conditions for Ring Opening ?

  • Gaebert, Carsten Fakultät für Chemie, Universität Bielefeld, Germany - Present address: Consortium für elektrochemische Industrie GmbH, München, Germany
  • Mattay, Jochen Fakultät für Chemie, Universität Bielefeld, Germany
  • Toubartz, Marion Max-Planck-Institut für Bioanorganische Chemie, Mülheim/Ruhr, Germany
  • Steenken, Steen Max-Planck-Institut für Bioanorganische Chemie, Mülheim/Ruhr, Germany
  • Müller, Beat Departement de Chimie, Université de Fribourg, Switzerland - Present address: Bundesamt für Umwelt, Wald und Landschaft, Bern, Switzerland
  • Bally, Thomas Departement de Chimie, Université de Fribourg, Switzerland
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    02.01.2005
Published in:
  • Chemistry - A European Journal. - 2005, vol. 11(4), no. 1294-1304
azomethine ylides
density functional calculations
matrix isolation
radical ions
reaction mechanisms
English Radical cations were generated from different phenyl-substituted aziridines by pulse radiolysis in aqueous solution containing TlOH.+, N₃. or SO₄.- as oxidants or in n-butyl chloride, by ⁶⁰Co γ radiolysis in Freon matrices at 77 K, and in some cases by flash photolysis in aqueous solution. Depending on the substitution pattern of the aziridines, two different types of radical cations are formed: if the N atom carries a phenyl ring, the aziridine appears to retain its structure after oxidation and the resulting radical cation shows an intense band at 440-480 nm, similar to that of the radical cation of dimethylaniline. Conversely, if the N atom carries an alkyl substituent while a phenyl ring is attached to a C-atom of the aziridine, oxidation results in spontaneous ring opening to yield azomethine ylide radical cations which have broad absorptions in the 500-800 nm range. In aqueous solution the two types of radical cations are quenched by O₂ with different rates, whereas in n-butyl chloride, the ring-closed aziridine radical cations are not quenchable by O₂. The results of quantum chemical calculations confirm the assignment of these species and allow to rationalize the different effects that phenyl rings have if they are attached in different positions of aziridines. In the pulse radiolysis experiments in aqueous solution, the primary oxidants can also be observed, whereas in n-butyl chloride a transient at 325 nm remains unidentified. In the laser flash experiments, both types of radical cations were also observed.
Faculty
Faculté des sciences et de médecine
Department
Département de Chimie
Language
  • English
Classification
Chemistry
License
License undefined
Identifiers
Persistent URL
https://folia.unifr.ch/unifr/documents/299563
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