From benzene to naphthalene: direct measurement of reactions and intermediates of phenyl radicals and acetylene

Abstract

First-time measurement of time evolution of the main products and critical intermediates on phenyl HACA pathways with a validated pressure-dependent model.

Theoretical study on the HACA chemistry of naphthalenyl radicals and acetylene: The formation of C12H8, C14H8, and C14H10 species

“…Indeed, their calculated energies are at least 43 kcal/mol more stable than 2‐C 10 H 7 + C 2 H 2 . At intermediate temperatures, resonance‐stabilized radicals with aromatic rings have been found to have longer lifetimes than other radicals 24 . Optimized geometries for species 1‐N14, 2‐N16, and 2‐N17 were previously reported by Park et al, 61 and we recalculated them at the G3(MP2,CC)//B3LYP/6‐311G ** level of theory, whereas to our knowledge 2‐N14 has not previously been reported in the literature.…”

“…Parker et al 32 suggested the intramolecular H‐transfer converting 2‐C 10 H 7 to 1‐C 10 H 7 must be fast to explain the formation of ACN from 2‐C 10 H 7 + C 2 H 2 . This process was considered in this work by including the pressure‐dependent reactions on the C 10 H 7 PES, including isomerization between 1‐C 10 H 7 and 2‐C 10 H 7 , from previously reported calculations 24,55 …”

“…Isomerization via direct intramolecular hydrogen transfer between 1‐naphthalenyl and 2‐naphthalenyl radical was pointed out by Parker et al, 32 which was proposed to possibly account for the ACN formation from 2‐naphthalenyl radical + C 2 H 2 . This isomerization is considered on the C 10 H 7 PES studied by Mebel et al 55 and Chu et al 24 and on the C 12 H 7 PES between N1‐CS12 and N1‐CS41 calculated here; the corresponding pressure‐dependent rate coefficients are incorporated into the model of this work.…”

“…Hydrogen‐abstraction‐C 2 H 2 ‐addition (HACA) routes 11,19–23 involving two C 2 H 2 additions to form an additional six‐member aromatic ring are among the most studied and important pathways. The HACA extension from the first to second ring leading to naphthalene has been widely studied experimentally 24–27 and theoretically, 28–31 and it has been recognized as the dominant pathway. However, further aromatic ring addition from naphthalene to phenanthrene (PTR) and anthracene (ANT) remains ambiguous at different temperature conditions.…”

Formation of phenanthrene via H‐assisted isomerization of 2‐ethynylbiphenyl produced in the reaction of phenyl with phenylacetylene

“…While the crucial feature of the HACA mechanism is the kinetic‐thermodynamic coupling of H abstraction and carbon addition steps and not the particular nature of the carbon species added, 2,5 in combustion environments under soot‐forming conditions, acetylene is believed to be the most essential growth species because of the high abundance in flames owing to its thermal stability 6‐12 . The “classical” acetylene‐based HACA mechanism is generally successful in kinetic modeling of the PAH growth in various flames and has been directly confirmed by molecular beam experiments in pyrolytic reactors for the formation of naphthalene from benzene, 13‐15 phenanthrene from biphenyl, and pyrene from phenanthrene 16,17 . However, according to theoretical calculations 18 and experiments in the pyrolytic reactor, 19 classical HACA does not produce benzenoid tricyclic PAHs phenanthrene and anthracene from bicyclic naphthalene under typical combustion conditions forming instead acenaphthylene with two six‐ and one five‐member ring.…”