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

Abstract

Model chemistry G3(MP2,CC)//B3LYP/6-311G(d,p) calculations of the potential energy surface for the reaction of phenyl radical (C 6 H 5) with phenylacetylene (C 8 H 6) have been carried out and combined with Rice-Ramsperger-Kassel-Marcus/Master Equation calculations of temperature-and pressure-dependent rate constants. The results showed that the reaction can serve as a viable source for the formation of phenanthrene via an indirect route involving a primary reaction of phenyl addition to the ortho carbon in the ring of phenylacetylene and H elimination producing 2-ethynylbiphenyl followed by secondary H-assisted isomerization of 2-ethynylbiphenyl to phenanthrene. In the secondary reaction, the H atom adds to the α carbon of the ethynyl side chain, then a six-member ring closure takes place followed by aromatization via an H loss. The channel of H addition to the side chain of 2-ethynylbiphenyl appears to be much faster than H addition to the ortho carbon in the ethynyl-substituted ring leading back to the initial C 6 H 5 + C 8 H 6 reactants. Rate constants for the primary C 6 H 5 + C 8 H 6 ← → 2ethynylbiphenyl (p1) + H and secondary p1 + H ← → phenanthrene (p2) + H reactions have been computed in the temperature range of 500-2500 K at pressures of 30 Torr, 1, 10, and 100 atm and fitted to modified Arrhenius expressions. The suggested kinetic scheme and rate constants are proposed as a prototype for the modeling of the growth of polycyclic aromatic hydrocarbons via the phenyl additiondehydrocyclization (PAC) mechanism involving an addition of a PAH radical to an ethynyl-substituted PAH molecule.

Catalytic Hydrogenation of Anthracene on Binary (Bimetallic) Composite Catalysts

“…However, Fe-Co/CaA has a greater hydrogenation capacity, i.e., the total content of degradation products is about 2%, but their total fraction was ~15% for Fe-Co/ZSM-5. The appearance of phenanthrene in products of anthracene hydrogenation using Fe-Co/CaA and Fe-Co/ZSM-5 may be related to isomerization of 2-ethylbiphenyl under the influence of hydrogen [56]. Table 2 describes that using the Fe-Co/ZSM-5, the degradation products consist mostly of 2-ethylbiphenyl, which is probably a source of phenanthrene formation.…”

IR/UV Double Resonance Study of the 2‐Phenylallyl Radical and its Pyrolysis Products

“…Furthermore, the addition of phenyl to phenylacetylene (see Figure S6 in the Supporting Information) via four‐membered ring intermediates as a variation of the PAC mechanism [24,38] was reported as another efficient route [39] . Recently, the route was predicted to preferentially proceed via the formation of 2‐ethynylbiphenyl by PAC, followed by H‐assisted isomerization to phenanthrene [40] . Considering the significant amounts of phenyl in the reactor, this reaction is expected to occur.…”

“…[39] Recently, the route was predicted to preferentially proceed via the formation of 2-ethynylbiphenyl by PAC, followed by H-assisted isomerization to phenanthrene. [40] Considering the significant amounts of phenyl in the reactor, this reaction is expected to occur. The less stable isomer anthracene has not been observed (see Figure 4c).…”

Phenalenyl growth reactions and implications for prenucleation chemistry of aromatics in flames

“…The values of n = 0.62 and a 300 = 424 cm À1 in this expression were earlier derived from classical trajectory calculations 43,44 and, along with the Lennard-Jones parameters e = 390 cm À1 and s = 4.46 Å, were adopted from our earlier studies of the growth kinetics of two-and three-ring PAHs, including the studies of C 2 H 2 addition reactions to various PAH radicals. 21,[45][46][47][48][49][50]…”