Brusa, M. A. and Colussi, A. J. (1982) Anomalous kinetic hydrogen isotope effect in the oxidation of formate by bromine: Tunneling via an intermediate. International Journal of Chemical Kinetics, 14 (11). pp. 1211-1218. ISSN 0538-8066. doi:10.1002/kin.550141105. https://resolver.caltech.edu/CaltechAUTHORS:20150803-152424653
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Abstract
Rates of oxidation of XCOO^− (X = H, D) by Br_2 in acid aqueous media were measured between 274 and 332 K. The derived Arrhenius parameters for both reactions log k_H(M^(-1) s^(-1) = (18.81 ± 0.10) - (14.33 ± 0.13)/ø log k_D(M^(-1) s^(-1) = (13.77 ± 0.13) - (17.62 ± 0.04)/ø where θ = 4.575T × 10^(−3) kcal/mol, with (k_H/k_D)_(298K) = 2.85, reveal a primary isotope effect, but the difference (E_D - E_H) = 3.29 kcal/mol and the ratio A_D/A_H = 91 fall beyond the limits imposed by semiclassical transition-state theory, suggesting tunneling or a multiple-stage mechanism. However, it can be shown that either tunneling in a single step or a three-step, internal return mechanism can be ruled out as alternative models, since both require unreasonable kinetic parameters to fit the data. The simplest scheme accounting for the present observations involves tunneling in the decomposition of a charge transfer complex in equilibrium with the reactants.
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| Additional Information: | © 1982 John Wiley & Sons. Received December 8, 1981, Accepted June 4, 1982. This work was supported by the Comisión de Investigaciones Científicas de Ia Provincia de Buenos Aires. | |||||||||
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| Issue or Number: | 11 | |||||||||
| DOI: | 10.1002/kin.550141105 | |||||||||
| Record Number: | CaltechAUTHORS:20150803-152424653 | |||||||||
| Persistent URL: | https://resolver.caltech.edu/CaltechAUTHORS:20150803-152424653 | |||||||||
| Official Citation: | Brusa, M. A. and Colussi, A. J. (1982), Anomalous kinetic hydrogen isotope effect in the oxidation of formate by bromine: Tunneling via an intermediate. Int. J. Chem. Kinet., 14: 1211–1218. doi: 10.1002/kin.550141105 | |||||||||
| Usage Policy: | No commercial reproduction, distribution, display or performance rights in this work are provided. | |||||||||
| ID Code: | 59156 | |||||||||
| Collection: | CaltechAUTHORS | |||||||||
| Deposited By: | George Porter | |||||||||
| Deposited On: | 05 Aug 2015 22:19 | |||||||||
| Last Modified: | 10 Nov 2021 22:15 |
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