New results for the oxidation of alkanes, alkenes, and alkylbenzenes by t-BuOOH according to the Kharasch reaction and Mn(III)— and Fe(III)—porphyrin catalysis are reported. Chemical and kinetic evidence show the role of t-BuO* and t-BuOO· radicals in these oxidations and the strict relationship with the Gif reaction, for which recently a free-radical mechanism has been emphasized in contrast with the Barton interpretation. A key step appears to be the hydrogen abstraction from t-BuOOH by t-BuO· very fast in nonbasic solvents, but inhibited by solvents which form hydrogen bonds with t-BuOOH. As a consequence, the generally accepted Kochi mechanism of the Kharasch reaction must be modified, and the similar mechanistic features of the three types of catalysis (Kharasch, metalloporphyrins, and Gif) are discussed.
(1995). Kharasch and Metalloporphyrin Catalysis in the Functionalization of Alkanes, Alkenes, and Alkylbenzenes by t-BuOOH. Free Radical Mechanisms, Solvent Effect, and Relationship with the Gif Reaction [journal article - articolo]. In JOURNAL OF THE AMERICAN CHEMICAL SOCIETY. Retrieved from https://hdl.handle.net/10446/232224
Kharasch and Metalloporphyrin Catalysis in the Functionalization of Alkanes, Alkenes, and Alkylbenzenes by t-BuOOH. Free Radical Mechanisms, Solvent Effect, and Relationship with the Gif Reaction
Fontana, Francesca;
1995-01-01
Abstract
New results for the oxidation of alkanes, alkenes, and alkylbenzenes by t-BuOOH according to the Kharasch reaction and Mn(III)— and Fe(III)—porphyrin catalysis are reported. Chemical and kinetic evidence show the role of t-BuO* and t-BuOO· radicals in these oxidations and the strict relationship with the Gif reaction, for which recently a free-radical mechanism has been emphasized in contrast with the Barton interpretation. A key step appears to be the hydrogen abstraction from t-BuOOH by t-BuO· very fast in nonbasic solvents, but inhibited by solvents which form hydrogen bonds with t-BuOOH. As a consequence, the generally accepted Kochi mechanism of the Kharasch reaction must be modified, and the similar mechanistic features of the three types of catalysis (Kharasch, metalloporphyrins, and Gif) are discussed.File | Dimensione del file | Formato | |
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