Theoretical, Experimental, and Modeling Study of the Reaction of Hydrogen Atoms with 1- and 2‑Pentene

Alkyl radicals are
prominent in combustion chemistry as they are
formed by hydrocarbon decomposition or from a radical attack on hydrocarbons.
Accurate determinations of the thermochemistry and kinetics of their
unimolecular isomerization and decomposition reactions and related
addition reactions of alkenes are therefore important in simulating
the combustion chemistry of virtually all hydrocarbon fuels. In this
work, a comprehensive potential energy surface (PES) for Ḣ-atom
addition to and abstraction from 1- and 2-pentene, and the subsequent
C–C and C–H β-scission reactions, and H-atom transfer
reactions has been considered. Thermochemical values for the species
on the Ċ5H11 PES were calculated as a
function of temperature (298–2000 K), with enthalpies of formation
determined using a network of isodesmic reactions. High-pressure limiting
and pressure-dependent rate constants were calculated using the Rice-Ramsperger-Kassel-Marcus
theory coupled with a one-dimensional master equation. As a validation
of our theoretical results, hydrogen atomic resonance absorption spectrometry
experiments were performed on the Ḣ-atom addition and abstraction
reactions of 1- and 2-pentene. By incorporating our calculations into
a detailed chemical kinetic model (AramcoMech 3.0), excellent agreement
with these experiments is observed. The theoretical results are further
validated via a comprehensive series of simulations of literature
data. Our a priori model is found to reproduce important
absolute species concentrations and product ratios reported therein.