Exotic Reaction Dynamics in the Gas-Phase Preparation of Anthracene (C₁₄H₁₀) via Spiroaromatic Radical Transients in the Indenyl–Cyclopentadienyl Radical–Radical Reaction

Abstract

The gas-phase reaction between the 1-indenyl (C 9 H 7 • ) radical and the cyclopentadienyl (C 5 H 5• ) radical has been investigated for the first time using synchrotron-based mass spectrometry coupled with a pyrolytic reactor. Soft photoionization with tunable vacuum ultraviolet photons afforded for the isomerselective identification of the production of phenanthrene, anthracene, and benzofulvalene (C 14 H 10 ). The classical theory prevalent in the literature proposing that radicals combine only at their specific radical centers is challenged by our discovery of an unusual reaction pathway that involves a barrierless combination of a resonantly stabilized hydrocarbon radical with an aromatic radical at the carbon atom adjacent to the traditional C1 radical center; this unconventional addition is followed by substantial isomerization into phenanthrene and anthracene via a category of exotic spiroaromatic intermediates. This result leads to a deeper understanding of the evolution of the cosmic carbon budget and provides new methodologies for the bottom-up synthesis of unique spiroaromatics that may be relevant for the synthesis of more complex aromatic carbon skeletons in deep space.

In search of universalities in the dissociative photoionization of PANHs via isomerizations

“…63 Indenyl, which is assigned to the dominant 115 peak in MeQ and Npa, in its neutral form is a resonance stabilized radical, which is known to be important precursors in PAH growth 64 in conditions relevant to interstellar chemistry. More specifically, reactions of indenyl with other smaller hydrocarbons have led to the formation of naphthalene, 65 phenanthrene, anthracene, benzofulvalene, 66 and other bigger organics. 67 Dissociative recombination with electrons of HCNH+ (which in its neutral form is produced profusely in the current experiment from the photodissociation of Npa and MeQ) is proposed to be one of the important sources for both HCN and HNC in the interstellar medium.…”

Efficient Oxidative Decomposition of Jet-Fuel exo-Tetrahydrodicyclopentadiene (JP-10) by Aluminum Nanoparticles in a Catalytic Microreactor: An Online Vacuum Ultraviolet Photoionization Study

“…The thermal decomposition of JP-10 over AlNP was explored at the Chemical Dynamics Beamline (9.0.2.) of the Advanced Light Source (ALS) utilizing a high-temperature catalytic microreactor ,, (Figure ). Briefly, the high-temperature microreactor consists of a resistively heated silicon carbide (SiC) tube of a 20 mm length and a 1 mm inner diameter, which was tightly packed with 80 nm sized aluminum nanoparticles (AlNP) over a length of 10 mm centered inside the SiC tube supported by a glass-wool bed (see the extended description and characterization of this reactor in Supporting Information, S1).…”

“…Additionally, the lack of a comprehensive inventory of temperature-dependent products and intermediates restricts a proper understanding of the underlying chemistry of such fuel additives, influencing the combustion properties of JP-10. Therefore, in the present study, we exploit an isomer-selective in situ diagnostics study utilizing photoionization to probe the reaction products in a molecular beam at temperatures ranging from 300 to 1400 K. This approach utilizes the power of soft photoionization with single-photon synchrotron vacuum ultraviolet (VUV) light followed by a mass spectroscopic analysis of the ions in a reflectron time-of-flight mass spectrometer (Re-TOF-MS). ,, The molecular beam was prepared by seeding JP-10 vapor in a helium (He)–oxygen (O 2 ) gas mixture at an 80 to 20% volume ratio and passing this mixture over AlNP within a chemical microreactor (Figure ). To elucidate the effects of the AlNP, the high-temperature oxidation of pure JP-10 was also conducted as a reference system within the same reactor at identical conditions but without the presence of AlNP.…”

“…Therefore, in the present study, we exploit an isomer-selective in situ diagnostics study utilizing photoionization to probe the reaction products in a molecular beam at temperatures ranging from 300 to 1400 K. This approach utilizes the power of soft photoionization with single-photon synchrotron vacuum ultraviolet (VUV) light followed by a mass spectroscopic analysis of the ions in a reflectron time-of-flight mass spectrometer (Re-TOF-MS). 15,33,34 The molecular beam was prepared by seeding JP-10 vapor in a helium (He)−oxygen (O 2 ) gas mixture at an 80 to 20% volume ratio and passing this mixture over AlNP within a chemical microreactor (Figure 1).…”

Gas‐Phase Preparation of the 14π Hückel Polycyclic Aromatic Anthracene and Phenanthrene Isomers (C14H10) via the Propargyl Addition–BenzAnnulation (PABA) Mechanism

“…Overall barrierless pathways are color coded in blue. [21,24,[40][41] produced from the hydrogen loss and hydrogen atom addition products of the 1'-/2'-naphthylmethyl radicals (Supplementary Information Figures S2 and S3).…”