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Hydrogen atom transfer (HAT) processes promoted by the quinolinimide-N-oxyl radical: a kinetic and theoretical study

  • DiLabio, Gino A. Department of Chemistry, University of British Columbia, Kelowna, British Columbia, Canada
  • Franchi, Paola Dipartimento di Chimica “G. Ciamician”, Università di Bologna, Italy
  • Lanzalunga, Osvaldo Dipartimento di Chimica, Sapienza Università di Roma and Istituto CNR di Metodologie Chimiche, Sapienza Università di Roma, Italy
  • Lapi, Andrea Dipartimento di Chimica, Sapienza Università di Roma and Istituto CNR di Metodologie Chimiche, Sapienza Università di Roma, Italy
  • Lucarini, Fiorella Département de Chimie, Université de Fribourg, Switzerland
  • Lucarini, Marco Dipartimento di Chimica “G. Ciamician”, Università di Bologna, Italy
  • Mazzonna, Marco Dipartimento di Chimica, Sapienza Università di Roma and Istituto CNR di Metodologie Chimiche, Sapienza Università di Roma, Italy
  • Prasad, Viki Kumar Department of Chemistry, University of British Columbia, Kelowna, British Columbia, Canada
  • Ticconi, Barbara Dipartimento di Chimica, Sapienza Università di Roma and Istituto CNR di Metodologie Chimiche, Sapienza Università di Roma, Italy
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    16.06.2017
Published in:
  • The Journal of Organic Chemistry. - 2017, vol. 82, no. 12, p. 6133–6141
English A kinetic study of the hydrogen atom transfer (HAT) reactions from a series of organic compounds to the quinolinimide-N-oxyl radical (QINO) was performed in CH3CN. The HAT rate constants are significantly higher than those observed with the phthalimide- N-oxyl radical (PINO) as a result of enthalpic and polar effects due to the presence of the N-heteroaromatic ring in QINO. The relevance of polar effects is supported by theoretical calculations conducted for the reactions of the two N-oxyl radicals with toluene, which indicate that the HAT process is characterized by a significant degree of charge transfer permitted by the π-stacking that occurs between the toluene and the N-oxyl aromatic rings in the transition state structures. An increase in the HAT reactivity of QINO was observed in the presence of 0.15 M HClO4 and 0.15 M Mg(ClO4)2 due to the protonation or complexation with the Lewis acid of the pyridine nitrogen that leads to a further decrease in the electron density in the N-oxyl radical. These results fully support the use of N-hydroxyquinolinimide as a convenient substitute for N-hydroxyphthalimide in the catalytic aerobic oxidations of aliphatic hydrocarbons characterized by relatively high C–H bond dissociation energies.
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/306103
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