Computational studies of reactions responsible for the formation and removal of phenyl radicals in hydrocarbon combustion

Detailed mechanisms for reactions of phenyl radicals with various hydrocarbons (methane, acetylene, ethylene, propylene, phenylacetylene and styrene) are elucidated using quantum-chemical methods to identify all kinetically important transition states and reactive intermediates. Several reactions relevant to the formation and destruction of phenyl radicals in hydrocarbon combustion are also studied. They include reactions of benzene with hydrogen atoms and hydroxyl, methyl and vinyl radicals, hydrogen addition to styrene, thermal decomposition of cyclopentadiene and the recombination of the cyclopentadienyl radical with hydrogen atom. Accurate thermochemistry is established for the key intermediates through isodesmic reaction analysis.; The kinetics for complex reactions with multiple intermediates, isomerization and decomposition channels is analyzed by comprehensive weak-collision master equation/Rice-Ramsperger-Kassel-Marcus modeling. Available experimental kinetic data is critically reviewed and correlated with the calculated rate constants. For the first time, the experimental total rate constants for the reactions of phenyl radicals with propylene, phenylacetylene and styrene have been measured by the cavity-ringdown spectrometry coupled with pulsed laser photolysis.; The results are important for understanding the formation and degradation mechanisms of aromatic hydrocarbons in combustion, atmospheric and interstellar environments.