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New results for the oxidation of alkanes, alkenes, and alkylbenzenesby t-BuOOH according to the Kharasch reaction and ()—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 byt-BuO", very fast in nonbasic solvents, but inhibited by solvents which form hydrogenbonds 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.