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Author(s):   Klippenstein, S.J.; Georgievskii, Y.; Harding, L.B.
Title:   Predictive theory for the combination kinetics of two alkyl radicals
Journal:   Phys. Chem. Chem. Phys.
Volume:   8
Page(s):   1133 - 1147
Year:   2006
Reference type:   Journal article
Squib:   2006KLI/GEO1133-1147

Reaction:   ·C2H5 + ·C2H5n-C4H10
Reaction order:   2
Temperature:   200 - 2000 K
Rate expression:   2.7x10-11 [cm3/molecule s] (T/298 K)-0.70 e13.30 [J/mole]/RT
Category:  Theory
Data type:   Transition state theory
Pressure dependence:   Rate constant is high pressure limit
Comments:   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.

View full bibliographic record.


Rate constant values calculated from the Arrhenius expression:

T (K)k(T) [cm3/molecule s]
200 3.60E-11
300 2.71E-11
400 2.21E-11
500 1.89E-11
600 1.66E-11
700 1.49E-11
800 1.36E-11
900 1.25E-11
1000 1.16E-11
1100 1.09E-11
1200 1.02E-11
1300 9.67E-12
1400 9.18E-12
1500 8.74E-12
1600 8.36E-12
1700 8.01E-12
1800 7.70E-12
1900 7.41E-12
2000 7.15E-12