How to add a five-membered ring to polycyclic aromatic hydrocarbons (PAHs) – molecular mass growth of the 2-naphthyl radical (C₁₀H₇) to benzindenes (C₁₃H₁₀) as a case study

Abstract

The reaction of aryl radicals with allene/methylacetylene leads to five-membered ring addition in PAH growth processes.

Gas-phase synthesis of corannulene – a molecular building block of fullerenes

“…Previous high-temperature circumstellar reaction networks borrowed from sooty hydrocarbon flames have revealed limited efficiencies under conditions prevailing in circumstellar envelopes to synthesize fullerenes predominantly due to the lack of constrained and validated mechanisms leading to PAHs and fullerenes. 58,62 These high temperature reaction mechanisms in carbon rich circumstellar envelopes are similaralbeit under the exclusion of oxygento the bottom-up formation of PAHs probed in sooting combustion flames of, e.g., methane, 63 acetylene, 64 and benzene 65 revealing the ubiquitous presence of aromatics like fluoranthene, benzo[ghi]fluoranthene, and corannulene along with fullerenes (C60,C70). The reaction pathways to corannulene revealed in the present study and the potential role of corannulene in the formation of fullerenes gain strong support from sophisticated examinations of carbonaceous chondrites.…”

Gas phase formation of phenalenevia10π-aromatic, resonantly stabilized free radical intermediates

“…The failed detection of p3 might be explained by its small photoionization cross section; interestingly, 1H-cyclopenta(a)naphthalene (p3) could not be detected in our earlier study of the 2-naphthyl -allene/methylacetylene systems, where its computed branching ratio is also similar to that of 3H-cyclopenta(a) naphthalene (p2). 38 As noted above, the alternative channel to form p2 via i17 is hindered by the high barrier for the i2 → i15 step. Besides i10, which is central to rationalize the formation of p1 and p2, intermediate i2 is of fundamental importance to understand the detection of acenaphthylene (C12H8) (p9) and 1-methylacenaphthalene (C13H10) (p8).…”

“…Each PIE curve reports the ion counts at a well-defined m/z ratio such as m/z = 166 as a function of the photon energy from 7.30 eV to 10.00 eV (Figure 2). The shapes of the PIE curves of C13H10 isomers-1H-phenalene, 3Hcyclopenta(a)naphthalene, 1-methylacenaphthylene are very different and therefore unique as recorded in separate calibration experiments within the same experimental setup under identical experimental conditions (Figure S1) 38 . A linear combination of these are used to fit the experimental PIE curves, shown for m/z = 165, 166, and 167 (Fig.…”

“…It shall be noted that under these experimental conditions, methylacetylene and allene do not isomerize to each other in the pyrolysis tube. 38,39 Detailed computational fluid dynamics (CFD) simulations of the gas flow in the microreactor suggest residence times of the reactants of a few 100 µs. 36,40,41 Typically, at the reaction center, this would give rise to a few tens collisions between the 1-naphthyl radical and the allene/methylacetylene molecules and/or between reaction products.…”

“…Tunneling corrections using asymmetric Eckart potentials were included in rate constant calculations. We employed collision parameters used by us earlier for RRKM-ME calculations of the prototype C6H5 + C3H4 49 and 1-naphthyl + C3H4 reactions; 38 the Lennard-Jones parameters were taken as (ε/cm −1 , σ/Å) = (390, 4.46) and the temperature dependence of the range parameter α for the deactivating wing of the energy transfer function was expressed as α(T) = α300(T/300 K) n , with n = 0.62 and α300 = 424 cm -1 . Calculations at p = 10 -10 atm emulating the zero-pressure limit took into account radiational stabilization of C13H11 intermediates.…”