Novel Products from C₆H₅ + C₆H₆/C₆H₅ Reactions

Abstract

To date only one product, biphenyl, has been reported to be produced from C(6)H(5) + C(6)H(6)/C(6)H(5) reactions. In this study, we have investigated some unique products of C(6)H(5) + C(6)H(6)/C(6)H(5) reactions via both experimental observation and theoretical modeling. In the experimental study, gas-phase reaction products produced from the pyrolysis of selected aromatics and aromatic/acetylene mixtures were detected by an in situ technique, vacuum ultraviolet (VUV) single photon ionization (SPI) time-of-flight mass spectrometry (TOFMS). The mass spectra revealed a remarkable correlation in mass peaks at m/z = 154 {C(12)H(10) (biphenyl)} and m/z = 152 {C(12)H(8) (?)}. It also demonstrated an unexpected correlation among the HACA (hydrogen abstraction and acetylene addition) products at m/z = 78, 102, 128, 152, and 176. The analysis of formation routes of products suggested the contribution of some other isomers in addition to a well-known candidate, acenaphthylene, in the mass peak at m/z = 152 (C(12)H(8)). Considering the difficulties of identifying the contributing isomers from an observed mass number peak, quantum chemical calculations for the above-mentioned reactions were performed. As a result, cyclopenta[a]indene, as-indacene, s-indacene, biphenylene, acenaphthylene, and naphthalene appeared as novel products, produced from the possible channels of C(6)H(5) + C(6)H(6)/C(6)H(5) reactions rather than from their previously reported formation pathways. The most notable point is the production of acenaphthylene and naphthalene from C(6)H(5) + C(6)H(6)/C(6)H(5) reactions via the PAC (phenyl addition-cyclization) mechanism because, until now, both of them have been thought to be formed via the HACA routes. In this way, this study has paved the way for exploring alternative paths for other inefficient HACA routes using the PAC mechanism.

Simulating X-ray photoelectron spectra with strong electron correlation using multireference algebraic diagrammatic construction theory

“…Benzynes are highly reactive intermediates that are commonly formed in organic and combustion reactions [143][144][145][146][147] and can act as precursors in the formation of polycyclic aromatic hydrocarbons. [148][149][150][151][152] Due to their open-shell singlet character, the electronic structure and properties of benzynes have been studied using a variety of quantum chemical methods. [153][154][155][156][157][158][159][160][161][162][163][164][165][166][167][168][169][170] All three molecules have the singlet ground electronic state with a significant diradical character that increases from ortho-to para-benzyne, 171,172 along with a decreasing singlet-triplet gap.…”

Polycyclic Aromatic Hydrocarbon Growth by Diradical Cycloaddition/Fragmentation

“…Yet new advances in computational capabilities represent a valuable resource for the implementation of investigations on novel potential energy surfaces for reactions between larger and larger compounds. In particular, recent theoretical studies highlight the presence of a relatively low pathway involving 1,4-cycloaddition of singlet o-benzyne to benzene and subsequent fragmentation to form naphthalene and acetylene 2,3 . This pathway seems to be energetically favorable compared to the addition step which proceeds through formation of a C-C bond followed by subsequent isomerization reactions.…”

“…This pathway seems to be energetically favorable compared to the addition step which proceeds through formation of a C-C bond followed by subsequent isomerization reactions. Based on the CBS-QB3 single-point energy calculations by Shukla et al 3 , the cycloaddition entrance barrier is around 10 kcal/mol lower than the addition barrier, although the latter may be affected by large uncertainties due to spin contamination. The pioneering experimental works on aryne compounds also indicate the reaction of o-benzyne and benzene (deuterated and not) as responsible for the formation of different PAH intermediates [4][5][6] .…”

Quantitative spectrochemical analysis of solution plasma in aromatic molecules

“…The reaction of the phenyl radical with benzene conducts to biphenyl, which has been confirmed by GC‐MS analysis. Biphenylene and fluorene can be formed from biphenyl or directly from benzene and phenyl . In SP in benzene, the presence of the phenyl radical was determined by emission spectroscopy and ESR in plasma gas and liquid phases, respectively.…”