ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Using H-atoms produced in the radiolysis of water vapour, we determined the kinetic isotope effect for the reaction \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm H}^{\rm .} + {\rm RH (R'D)}{\rm H}_{\rm 2} {\rm (HD) + R}^{\rm .} {\rm (R'}^{\rm .}) $$\end{document} where RH and R′D are methylcyclohexane and perdeuterated methylcyclohexane, respectively. The result obtained from the isotope competitive method can be expressed with the Arrhenius-type equation kH/kD = (0.51 ± 0.04) exp[(8.58 ± 0.25) kJ mol-1/RT] over the temperature range from 363 to 483 K. The occurrence of H abstraction from primary, secondary, and tertiary C—H bonds in methylcyclohexane is taken into consideration in the interpretation of the Arrhenius-type expression obtained. Theoretical interpretation of the kinetic isotope effect has been achieved on the basis of the transition-state theory and a semiempirical London-Eyring-Polanyi-Sato potential-energy surface. The tunnel effect is found to play a role in the H-abstraction. Several methods for estimating the tunnel correction factors have been discussed.
Additional Material:
7 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19850680512
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