Kinetics of the hydrogen abstraction ·C2H5 + alkane → C2H6 + alkyl reaction class: an application of the reaction class transition state theory

Abstract

This paper presents an application of the reaction class transition state theory (RC-TST) to predict thermal rate constants for hydrogen abstraction reactions at alkane by the ÁC 2 H 5 radical on-the-fly. The linear energy relationship (LER), developed for acyclic alkanes, was also proven to hold for cyclic alkanes. We have derived all RC-TST parameters from rate constants of 19 representative reactions, coupling with LER and the barrier height grouping (BHG) approach. Both the RC-TST/LER, where only reaction energy is needed, and the RC-TST/BHG, where no other information is needed, can predict rate constants for any reaction in this reaction class with satisfactory accuracy for combustion modeling. Our analysis indicates that less than 50 % systematic errors on the average exist in the predicted rate constants using either the RC-TST/LER or RC-TST/BHG method, while in comparison with explicit rate calculations, the differences are within a factor of 2 on the average. The results also show that the RC-TST method is not sensitive to the choice of density functional theory used.

Performance of First-Principles-Based Reaction Class Transition State Theory

“…As mentioned earlier, in general, very few experimental data are available. The detailed comparison of the RC-TST results with those available from other sources had been done for each application of the theory (see, for example, refs , − , , , , , , , , and ). The majority of experimental rates possess quoted uncertainty factors of less than 2.…”

“…Thus, the temperature dependence of f Q comes solely from the vibrational component. Furthermore, it was shown (see, for example, refs , , , , , and ) that the contributions to the vibrational partition functions from the principal components of the reactive moiety and of the substituents are canceled. Therefore, the main factors that govern the temperature dependence of the f Q factor are the differences in the vibrational frequencies due to the coupling of substituents with the reactive moiety.…”

Theoretical and kinetic study of the hydrogen atom abstraction reactions of ethyl esters with hydrogen radicals

“…For the tunneling effects, the asymmetrical Eckart tunneling corrections can give accurate results compared with multidimensional tunneling method [17,24]. The treatment of internal rotations for the H-abstraction reactions in this work is not carried out, since the effect of internal rotations is small and such approximation may only yield an error of about 10-20% in the final rate constants based on previous studies [25,26]. Thus, the effect of the internal rotations on the overall uncertainty of the final rate constants is small.…”

On-The-Fly Kinetics of the Hydrogen Abstraction by Hydroperoxyl Radical: An Application of the Reaction Class Transition State Theory

“…However, the errors (~40% maximum and ~13% averaged) are unexpectedly large when compared to similar reaction classes. For example, the average errors are about 5% for H abstraction by alkyl (Ratkiewicz et al, 2013) and 10% by hydroxyl (Huynh et al, 2006) radicals. This suggests the complicated nature of the tunneling phenomenon for the title family, which may be an interesting subject for further study.…”