Publication
552
J. Chem.
Soc., Perkin Trans2., 2002, (5),
985 - 990
DOI:
10.1039/b110994d |
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Thermodynamics
and kinetics of homolytic cleavage of carbon–oxygen
bonds in radical anions obtained by electrochemical
reduction of alkyl aryl ethers
|
Claude
P. Andrieux, Maria Farriol, Iluminada Gallardo and Jordi
Marquet
Laboratoire d'Electrochimie Moléculaire
de l'Université Denis Diderot (Paris 7), UMR
CNRS 7591, 2 place Jussieu, Tour 44–45, 75251
Paris Cedex 05, France
Departament de Química, Universitat Autònoma de Barcelona,
E-08193 Bellaterra, Barcelona, Spain
The properties and the reactivity of the radical
anions of 4-cyanophenyl alkyl ethers and naphthyl
alkyl ethers have been determined by electrochemical
methods. Under electrochemical conditions homolytic
dissociation is the only observed process. Cyclic
voltammetry studies lead to the conclusion that this
process is a stepwise one, the initially produced
radical anion cleaving by a slow first order reaction
followed by a second electron transfer in a DISP1
mechanism. A Marcus type relationship between the
cleavage rate constants and the standard free energy
of the reaction leads to an intrinsic barrier in
the range of 0.7 to 0.8 eV. The analysis of the intrinsic
barrier values indicates that solvent organisation
represents a modest contribution, the bond dissociation
energy of the radical anion (structural contribution)
being the main factor in the total barrier. Previously
unknown bond dissociation energies of naphthyl ethers
have been estimated using the correlations established
in this work. |
