| Autor: |
Krasnoukhov VS; Samara National Research University, Samara 443086, Russian Federation., Zagidullin MV; Lebedev Physical Institute, Samara 443011, Russian Federation., Zavershinskiy IP; Samara National Research University, Samara 443086, Russian Federation., Mebel AM; Samara National Research University, Samara 443086, Russian Federation.; Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, United States. |
| Jazyk: |
angličtina |
| Zdroj: |
The journal of physical chemistry. A [J Phys Chem A] 2020 Dec 03; Vol. 124 (48), pp. 9933-9941. Date of Electronic Publication: 2020 Nov 18. |
| DOI: |
10.1021/acs.jpca.0c09091 |
| Abstrakt: |
This work presents quantum chemical G3(MP2,CC)//B2PLYPD3/6-311G(d,p) calculations of the potential energy surface for the indenyl (C 9 H 7 ) + cyclopentadienyl (C 5 H 5 ) reaction followed by unimolecular decomposition of the C 14 H 11 radicals formed as the primary products, as well as the Rice-Ramsperger-Kassel-Marcus master equation (RRKM-ME) calculations to predict temperature- and pressure-dependent reaction rate constants and product branching ratios. The reaction begins with the barrierless recombination of indenyl and cyclopentadienyl forming a C 14 H 12 molecule with a new C-C bond connecting two five-membered rings, which subsequently dissociates to C 14 H 11 radicals by H losses. The primary products of the C 9 H 7 + C 5 H 5 → C 14 H 11 + H reaction can directly decompose by another H loss to benzofulvalene, and this pathway is most favorable in terms of the entropy factor and hence is preferable at higher temperatures. Otherwise, the initial C 14 H 11 isomers can undergo significant structural rearrangements before eliminating an H atom and producing phenanthrene, anthracene, or benzoazulenes, among which the formation of phenanthrene via the "spiran" pathway is clearly preferred. The calculated barriers along the computed favorable dissociation pathways are relatively low, in the ∼30-40 kcal/mol range, making the C 14 H 11 radicals unstable at temperatures above 1000-1250 K at 1 atm. The results of RRKM-ME calculations show that, under typical combustion conditions, the decomposition of the C 14 H 11 radicals predominantly leads to benzofulvalene. However, the latter can be rapidly converted to phenanthrene via H-assisted isomerization with the rate constant for the benzofulvalene + H → phenanthrene + H reaction being close to 10 -11 cm 3 molecule -1 s -1 at 1000-1500 K and 1 atm. The results provide further support for the hypothesis that recombination of two π radicals containing five-membered rings can lead to a growth of PAH with the formation of two fused six-membered rings, but the reaction mechanism may not be direct and is likely to involve two consecutive H atom losses leading to a fulvalene-like product, with subsequent H-assisted isomerization of the latter to a benzenoid PAH. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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