Hydrogen Atom Abstraction from C-H Bonds of Benzylamides by the Aminoxyl Radical BTNO: A Kinetic Study (Articolo in rivista)

Type
Label
  • Hydrogen Atom Abstraction from C-H Bonds of Benzylamides by the Aminoxyl Radical BTNO: A Kinetic Study (Articolo in rivista) (literal)
Anno
  • 2009-01-01T00:00:00+01:00 (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#doi
  • 10.1039/b815584d (literal)
Alternative label
  • A. Coniglio, C, Galli, P. Gentili, R. Vadalà (2009)
    Hydrogen Atom Abstraction from C-H Bonds of Benzylamides by the Aminoxyl Radical BTNO: A Kinetic Study
    in Organic & biomolecular chemistry
    (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
  • A. Coniglio, C, Galli, P. Gentili, R. Vadalà (literal)
Pagina inizio
  • 155 (literal)
Pagina fine
  • 160 (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#numeroVolume
  • 7 (literal)
Rivista
Note
  • ISI Web of Science (WOS) (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni
  • Dipartimento di Chimica, Universit`a 'La Sapienza', and IMC-CNR Sezione Meccanismi di Reazione (literal)
Titolo
  • Hydrogen Atom Abstraction from C-H Bonds of Benzylamides by the Aminoxyl Radical BTNO: A Kinetic Study (literal)
Abstract
  • The aminoxyl radical BTNO (benzotriazole-N-oxyl; >N-O?) is generated from HBT (1-hydroxybenzotriazole; >N-OH) by oxidation with a CeIV salt. BTNO presents a broad absorption band with lmax 474 nm that lends itself to investigate the kinetics of H-abstraction from H-donor substrates by spectrophotometry. Thus, rate constants (kH) of H-abstraction by BTNO from CH2-groups a to the nitrogen atom in X-substituted-(N-acetyl)benzylamines (X-C6H4CH2NHCOCH3) have been determined in MeCN solution at 25 oC. Correlation of the kH X data with the Hammett s+ parameters gives a small value for r (-0.65) that is compatible with a radical H-abstraction step. The sizeable value (kH/kD = 8.8) of the kinetic isotope effect from a suitably deuteriated amide substrate further confirms H-abstraction as rate-determining. Evidence is acquired for the relevance of stereoelectronic effects that speed up the H-abstraction whenever the scissile C-H bond is co-linear with either the nitrogen lone-pair of the amide moiety or an adjacent aromatic group. An assessment of the dissociation energy value of the benzylic C-H bond in ArCH2NHCOMe is accordingly reported (literal)
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