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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:   2-C3H7 + ·CH3iso-C4H10
Reaction order:   2
Temperature:   200 - 2000 K
Rate expression:   3.58x10-11 [cm3/molecule s] (T/298 K)-0.47 e812 [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 the 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 7.05E-11
300 4.94E-11
400 3.98E-11
500 3.41E-11
600 3.02E-11
700 2.75E-11
800 2.53E-11
900 2.36E-11
1000 2.22E-11
1100 2.11E-11
1200 2.01E-11
1300 1.92E-11
1400 1.84E-11
1500 1.78E-11
1600 1.72E-11
1700 1.66E-11
1800 1.61E-11
1900 1.57E-11
2000 1.52E-11