Rate and Driving Force for Protonation of Aryl Radical Anions in Ethanol
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- 作者：Alison M. Funston ; Sergei V. Lymar ; Barbara Saunders-Price ; Gidon Czapski ; John R. Miller
- 刊名：Journal of Physical Chemistry B
- 出版年：2007
- 出版时间：June 21, 2007
- 年：2007
- 卷：111
- 期：24
- 页码：6895 - 6902
- 全文大小：228K
- 年卷期：v.111,no.24(June 21, 2007)
- ISSN：1520-5207
文摘
Aryl radical anions created in liquid alcohols decay on the microsecond time scale by transfer of protonsfrom the solvent.1,2 This paper reports a 4.5 decade range of rate constants for proton transfer from a singleweak acid, ethanol, to a series of unsubstituted aryl radical anions, Ar-
. The rate constants correlate withfree energy change, 
G
, despite wide variations in the two factors that contribute to G: (a) the reductionpotentials of the aryls and (b) the Ar-H bond strengths in the product radicals. For aryl radical anionscontaining CH2OH substituents, such as 2,2'-biphenyldimethanol- which is protonated with a rate constantof 3 × 109 s-1, the faster rates do not fit well in the free energy correlation, suggesting a change in mechanism.
. The rate constants correlate withfree energy change, G, despite wide variations in the two factors that contribute to G: (a) the reductionpotentials of the aryls and (b) the Ar-H bond strengths in the product radicals. For aryl radical anionscontaining CH2OH substituents, such as 2,2'-biphenyldimethanol- which is protonated with a rate constantof 3 × 109 s-1, the faster rates do not fit well in the free energy correlation, suggesting a change in mechanism.