title: Role of electron-transfer processes in reactions of diarylcarbenium ions and related quinone methides with nucleophiles.
abstract: Second-harmonic alternating current voltammetry has been used to determine one-electron reduction potentials of 15 diarylcarbenium 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 = 14.091E degrees (red) - 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.
authors.affiliation: Department Chemie der Ludwig-Maximilians-Universität München, Butenandtstr 5-13 (Haus F), D-81377 München, Germany.
authors.forename: Armin R
authors.initials: AR
authors.lastname: Ofial
authors.forename: Kei
authors.initials: K
authors.lastname: Ohkubo
authors.forename: Shunichi
authors.initials: S
authors.lastname: Fukuzumi
authors.forename: Roland
authors.initials: R
authors.lastname: Lucius
authors.forename: Herbert
authors.initials: H
authors.lastname: Mayr