Mechanisms of hydrogen-, oxygen-, and electron-transfer reactions of cumylperoxyl radical

Shunichi Fukuzumi, Kanji Shimoosako, Tomoyoshi Suenobu, Yoshihito Watanabe

Research output: Contribution to journalArticlepeer-review

92 Scopus citations

Abstract

Rates of hydrogen-transfer reactions from a series of para-substituted N,N-dimethylanilines to cumylperoxyl radical and oxygen-transfer reactions from cumylperoxyl radical to a series of sulfides and phosphines have been determined in propionitrile (EtCN) and pentane at low temperatures by use of ESR. The observed rate constants exhibit first-order and second-order dependence with respect to concentrations of N,N-dimethylanilines. This indicates that the hydrogen- and oxygen-transfer reactions proceed via 1:1 charge-transfer (CT) complexes formed between the substrates and cumylperoxyl radical. The primary kinetic isotope effects are determined by comparing the rates of N,N-dimethylanilines and the corresponding N,N-bis(trideuteriomethyl)anilines. The isotope effect profiles are quite different from those reported for the P-450 model oxidation of the same series of substrates. Rates of electron-transfer reactions from ferrocene derivatives to cumylperoxyl radical have also been determined by use of ESR. The catalytic effects of Sc(OTf)3 (OTf = triflate) on the electron-transfer reactions are compared with those of Sc(OTf)3 on the hydrogen- and oxygen-transfer reactions. Such comparison provides strong evidence that the hydrogen- and oxygen- transfer reactions of cumylperoxyl radical proceed via a one-step hydrogen atom and oxygen atom transfer rather than via an electron transfer from substrates to cumylperoxyl radical.

Original languageEnglish
Pages (from-to)9074-9082
Number of pages9
JournalJournal of the American Chemical Society
Volume125
Issue number30
DOIs
StatePublished - 30 Jul 2003

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