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Applied Chemicals and Materials Division
Klippenstein, S.J.; Georgievskii, Y.; Harding, L.B.
Predictive theory for the combination kinetics of two alkyl radicals
Phys. Chem. Chem. Phys.
1133 - 1147
tert-C4H9 + ·C2H5 → (CH3)3CCH2CH3
200 - 2000
1.73x10-11 [cm3/molecule s] (T/298 K)-0.89 e608 [J/mole]/RT
Transition state theory
Rate constant is high pressure limit
Rate constants were calculated with an ab initio transition state theory employing direct evaluations of the orientation dependent interaction energies at the CASPT2/cc-pvdz level within variable reaction
coordinate transition state theory (VRC-TST). Results were compared with experiment for a series of alkyl radicals and good quantitative agreement was found.
Each methyl substituent adjacent to a radical site was found to reduce the rate coefficient by about a factor of two. Rate constants are predicted to decrease substantially with increasing temperature, with the more sterically hindered reactants having a more rapid decrease. The geometric mean rule was found to be in good agreement with the detailed calculations.
The authors state the rate parameters are strictly applicable between 200-2000 K but that they should provide reasonable predictions up to about 2700 K.
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Rate constant values calculated from the Arrhenius expression:
|T (K)||k(T) [cm3/molecule s]|