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Titolo:
The thermal sulfenate-sulfoxide rearrangement: A radical pair mechanism
Autore:
Amaudrut, J; Wiest, O;
Indirizzi:
Univ Notre Dame, Dept Chem & Biochem, Notre Dame, IN 46556 USA Univ Notre Dame Notre Dame IN USA 46556 Biochem, Notre Dame, IN 46556 USA
Titolo Testata:
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
fascicolo: 14, volume: 122, anno: 2000,
pagine: 3367 - 3374
SICI:
0002-7863(20000412)122:14<3367:TTSRAR>2.0.ZU;2-Y
Fonte:
ISI
Lingua:
ENG
Soggetto:
CARBON-CENTERED RADICALS; GENERATION; KINETICS; DISSOCIATION; PHOTOLYSIS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Physical, Chemical & Earth Sciences
Citazioni:
40
Recensione:
Indirizzi per estratti:
Indirizzo: Wiest, O Univ Notre Dame, Dept Chem & Biochem, Notre Dame, IN 46556 USA Univ Notre Dame Notre Dame IN USA 46556 Notre Dame, IN 46556 USA
Citazione:
J. Amaudrut e O. Wiest, "The thermal sulfenate-sulfoxide rearrangement: A radical pair mechanism", J AM CHEM S, 122(14), 2000, pp. 3367-3374

Abstract

The thermal reaction of sulfenates (RS-OR), yielding their corresponding sulfoxides (RS(=O)R), was studied experimentally. The first step of the reaction was found to be the formation a radical pair by homolytic cleavage of the carbon-oxygen bond of the sulfenate. The two transient radicals formed then recombine to form the carbon-sulfur bond of the sulfoxide. The thermolysis of cinnamyl-4-nitrobenzenesulfenate has a positive entropy of activation (Delta S = 6.4 +/- 2.0 eu in toluene), characteristic of a dissociative pathway, A normal secondary kinetic isotope effect (k(H)/k(D) = 1.19 +/- 0.04) was also measured with this substrate, Finally, a trapping experiment allowed the isolation and characterization of a product coming from the coupling of the cinnamyl radical and TEMPO, These studies confirm a mechanism that was proposed earlier based on computational studies. The experimentallydetermined bond dissociation energy of the carbon-oxygen bond of similar to 28 kcal.mol(-1) is in good agreement with the computed value of similar to 26 kcal.mol(-1). These studies confirm a unique structural feature of thesulfenate moiety, where the weakest bond of the molecule in the ground state is not the heteroatom-heteroatom bond intuitively considered to be the weakest based on the analogy to peroxides or disulfides. Radical stabilizingsubstituents are expected to have a large effect on the thermal reactivityof sulfenates. Evidence for a competing acid-catalyzed mechanism has also been observed.

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Documento generato il 04/12/20 alle ore 16:36:14