Role of electron-transfer processes in reactions of diarylcarbenium ions and related quinone methides with nucleophiles

被引:43
|
作者
Ofial, AR
Ohkubo, K
Fukuzumi, S
Lucius, R
Mayr, H
机构
[1] Univ Munich, Dept Chem, D-81377 Munich, Germany
[2] Japan Sci & Technol Corp, JST, CREST, Osaka Univ,Grad Sch Engn,Dept Mat & Life Sci, Suita, Osaka 5650871, Japan
关键词
D O I
10.1021/ja035191v
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
Second-harmonic alternating current voltammetry has been used to determine one-electron reduction potentials of 15 diarylcarbeniurn ions and 5 structurally analogous quinone methides, which have been employed as reference electrophiles for the development of nucleophilicity scales. A linear correlation (r(2) = 0.993) between the empirical electrophilicity parameters E and the reduction potentials in acetonitrile (E = 14.091 E-red(o) - 0.279) covering a range of 1.64 V (or 158 kJ mol(-1)) has been observed. For a large number of nucleophiles, it has been demonstrated that the observed activation free energies of the electrophile-nucleophile combinations are 61-195 kJ mol(-1) smaller than the free energy change of electron transfer from nucleophile to electrophile, which definitely excludes outer-sphere electron transfer occurring during these reactions.
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页码:10906 / 10912
页数:7
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