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On the slope of free energy plots in chemical kinetics

Cohen, Audrey O. and Marcus, R. A. (1968) On the slope of free energy plots in chemical kinetics. Journal of Physical Chemistry, 72 (12). pp. 4249-4256. ISSN 0022-3654. doi:10.1021/j100858a052.

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In current electron-transfer theory, an activation free energy term, ΔF*, depends in a simple way on the “standard” free energy of reaction, ΔF^0’, in the prevailing medium. Namely, ΔF* = (1/4)λ[1 + (ΔF^0’/λ)]^2, apart from small work terms; λ/4 is ΔF_0*, the value of ΔF* at (ΔF^0’ = 0; and λ obeys a simple additivity property. As an exploratory step an equation of the same functional form is applied in the present paper to data on Brønsted slopes of 16 proton- and atom-transfer reaction series. Thereby, the instantaneous slope of a ΔF* vs. ΔF^0’ plot is calculated to be (1/2)[1 + (ΔF^0’/4 ΔF_0*)]. Thus far the experimental results are consistent with this equation, but more data are needed. Other applications of the ΔF* equation, including one to the kinetic isotope effect, are also discussed. A rather approximate derivation of the above equation for atom and other transfers was given in an earlier paper of this series.

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Marcus, R. A.0000-0001-6547-1469
Additional Information:© 1968 American Chemical Society. (Received June 6, 1968) Acknowledgment is made to the donors of the Petroleum Research Fund, administered by the American Chemical Society, for partial support of this research. This research was also supported by a grant from the National Science Foundation at the University of Illinois.
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American Chemical Society Petroleum Research FundUNSPECIFIED
Issue or Number:12
Record Number:CaltechAUTHORS:20150817-152550488
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Official Citation:Slope of free energy plots in chemical kinetics Audrey O. Cohen and Rudolph A. Marcus The Journal of Physical Chemistry 1968 72 (12), 4249-4256 DOI: 10.1021/j100858a052
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:59661
Deposited By: George Porter
Deposited On:17 Aug 2015 23:06
Last Modified:10 Nov 2021 22:23

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