Kinetics of the cyclopentadienyl + acetylene, fulvenallene + H, and 1-ethynylcyclopentadiene + H reactions.
Quantum chemical methods and statistical reaction rate theory are utilized to examine the kinetics and thermochemistry of three reactions occurring on the C(7)H(7) potential energy surface: cyclopentadienyl (C(5)H(5)) + acetylene (C(2)H(2)), fulvenallene + H, and 1-ethynylcyclopentadiene + H. These reactions are relevant to the formation of polyaromatic hydrocarbons (PAHs) and the combustion of alkylated aromatics. Reaction of the resonantly stabilized C(5)H(5) radical with C(2)H(2) is an important PAH growth reaction; here we identify several new low-energy pathways connecting these reactants with fulvenallene + H, 1-ethynylcyclopentadiene + H, and the cycloheptatrienyl and benzyl radicals. The chemically activated C(5)H(5) + C(2)H(2) reaction is shown to form cycloheptatrienyl at low temperatures along with minor amounts of benzyl, which is the current evaluation in the literature. However, at typical combustion temperatures the C(7)H(6) isomers 1-ethynylcyclopentadiene and fulvenallene are the main products. The fulvenallene + H reaction predominantly forms benzyl (among other C(7)H(7) isomers), whereas the 1-ethynylcyclopentadiene reaction leads to C(5)H(5) + C(2)H(2) and fulvenallene + H as the major products. The resonantly stabilized vinylcyclopentadienyl radical is formed in both C(7)H(6) + H processes and is proposed here as a significant C(7)H(7) combustion intermediate. The reactions described here are believed to account for the C(7)H(6) products observed in cyclopentene combustion, where we suggest they are a mixture of 1-ethynylcyclopentadiene and fulvenallene. The C(7)H(6) + H reactions provide a mechanism for the conversion of 1-ethynylcyclopentadiene to fulvenallene and fulvenallene to benzyl.
da Silva
Gabriel
G
Department of Chemical and Biomolecular Engineering, The University of Melbourne, Victoria 3010, Australia. gdasilva@unimelb.edu.au
Cole
John A
JA
Bozzelli
Joseph W
JW
D000114:Acetylene / Q000737:chemistry*; D000466:Alkadienes / Q000737:chemistry*; D003198:Computer Simulation; D003517:Cyclopentanes / Q000737:chemistry*; D006841:Hydrocarbons, Aromatic / Q000138:chemical synthesis / Q000737:chemistry; D007700:Kinetics; D011789:Quantum Theory; D013696:Temperature
D000466:Alkadienes; D003517:Cyclopentanes; D006841:Hydrocarbons, Aromatic; C548922:fulvenallene; D000114:Acetylene