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The use of transition‐state theory to extrapolate rate coefficients for reactions of H atoms with alkanes
Author(s) -
Cohen N.
Publication year - 1991
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550230804
Subject(s) - isobutane , chemistry , neopentane , cyclopropane , thermodynamics , propane , cyclopentane , alkane , pentane , transition state theory , butane , atmospheric temperature range , cyclohexane , isochoric process , transition state , methane , computational chemistry , kinetics , reaction rate constant , hydrocarbon , organic chemistry , molecule , catalysis , ring (chemistry) , physics , quantum mechanics
The thermochemical kinetics formulation of conventional transition state theory has been applied to metathesis reactions of H atoms with a series of alkanes in order to provide a sound framework for the intercomparison of experimental data, and also to extrapolate rate coefficients to temperature regimes that may lie beyond the range of experiments. The calculations require a value for the rate coefficient at some temperature, necessitating a discussion of the extant experimental data and their reliability. The procedures are described, the results of the calculations are presented, and their agreement with experimental data (for methane, ethane, propane, butane, pentane, isobutane, cyclopropane, cyclohexane, neopentane, neooctane, and 2,2,3‐trimethylbutane) is discussed. A general expression for reactions of H with large (more than 4 carbons) alkanes is proposed:\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{rcl} k({\rm T}) &=& 5.4\, \times\, 10^3 n_p {\rm T}^{{\rm 2.0}} \exp (- 3540/{\rm T)}\, +\, 4.7\, \times\, 10^3 n_s {\rm T}^{{\rm 2}{\rm .2}} \exp (- 2640/{\rm T)}\\ \,\,&+&\, 3.7\, \times\, 10^3 n_t {\rm T}^{{\rm 2}{\rm .0}} \exp (- 970/{\rm T),} \end{array} $$\end{document} where n p , n s , and n t are the numbers of primary, secondary, and tertiary H atoms available for abstraction.