First-principles kinetics of n-octyl radicals

Abstract

Kinetics of the isomerisation and unimolecular degradation of n-octyl radicals have been studied with the reaction class transition state theory (RC-TST) method. To explore the kinetics of the 1,7-H migration reactions family, the accurate high-pressure limits of the rate constants for the reference reaction of this class (1-heptyl → 1-heptyl) have been calculated. Finally, both the achievements reported in this paper and previous developments are employed to obtain theoretical branching ratios of intramolecular H-transfers and unimolecular degradations of all possible n-octyl radicals; the results are in satisfactory agreement when compared to experiment. The application of the rates obtained to the simulation of a simple reactor is also reported.

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

“…Such a selection is given by both the importance of the octane, which is one of the constituents of the gasoline, as well as the availability of the experimental data to compare with the RC-TST results. Furthermore, high pressure limits of the rates constants and values of particular factors of all possible H-transfers and unimolecular degradations of octyl radicals had been calculated …”

“…Furthermore, high pressure limits of the rates constants and values of particular factors of all possible H-transfers and unimolecular degradations of octyl radicals had been calculated. 90 The multichannel nature of this reaction is complicated. Particularly, there are four isomeric octyl radicals that can undergo six beta bond fission reactions and a number of different reversible H-transfer isomerization processes.…”

“…Although Figure 8 seems to reveal larger errors in the predicted values, macroscopic simulations based on theoretical and experimental data from Figure 8 did not show significant differences. 90 Note that experimentally nondetectable thermoneutral H migrations also affect the total (i.e., summed over all four radicals) ratios of the particular channels.…”

Predicting isotopologue abundances in the products of organic catagenesis with a kinetic Monte-Carlo model

“…For radical isomerization (H-migration), we assign kinetic parameters to each reaction based on its migration distance. We allow migration from the radical position (1) to the 4, 5 6, or 7 positions (number indexed by distance to the radical position), because the migration of other distances are at least 3 orders of magnitude slower (Ratkiewicz et al, 2010;Sirjean et al, 2012;Ratkiewicz, 2013). The library data contain sets of kinetic parameters specific for migrations to the 4,5 and 6 positions.…”