Issue 16, 2024

Bridging the gap: viable reaction pathways from tetrahedrane to benzyne

Abstract

The addition of sp-carbon-containing molecules to polycyclic sp3 tetrahedrane (c-C4H4) results in the formation of both o-benzyne (c-C6H4) and benzene (c-C6H6). Since both c-C6H4 and c-C6H6 have been detected in the interstellar medium (ISM), providing additional pathways for their possible astrochemical formation mechanisms can lead to the discovery of other molecules, such as c-C4H4, benzvalyne, and vinylidene (:CCH2). Addition of diatomic carbon (C2), the ethynyl radical (C2H), vinylidene, and acetylene (HC[triple bond, length as m-dash]CH) to c-C4H4 is undertaken in individual pathways through high-level quantum chemical computations at the CCSD(T)-F12b/cc-pVTZ-F12 level of theory. The resulting C2 addition pathway proceeds barrierlessly through benzvalyne as an intermediate and reaches a true minimum at c-C6H4, but no leaving groups are produced which is required to dissipate excess energy within an interstellar chemical scheme. Similarly, the C2H addition to c-C4H4 produces benzvalyne as well as its related isomers. This pathway allows for the loss of a hydrogen leaving group to dissipate the resulting energy. Lastly, the HC[triple bond, length as m-dash]CH and :CCH2 addition pathways follow through both benzvalene and benzvalyne in order to reach c-C6H6 (benzene) and c-C6H4 (o-benzyne) as well as H2 as the required leaving group. Although there is a barrier to the HC[triple bond, length as m-dash]CH addition, the :CCH2 addition presents the contrary with only submerged barriers. These proposed mechanisms provide alternative possibilities for the formation of complex organic molecules in space.

Graphical abstract: Bridging the gap: viable reaction pathways from tetrahedrane to benzyne

Supplementary files

Article information

Article type
Paper
Submitted
20 ဒီ 2023
Accepted
05 ဧပြီ 2024
First published
08 ဧပြီ 2024

Phys. Chem. Chem. Phys., 2024,26, 12510-12519

Bridging the gap: viable reaction pathways from tetrahedrane to benzyne

T. A. Cole, S. R. Davis, A. R. Flint and R. C. Fortenberry, Phys. Chem. Chem. Phys., 2024, 26, 12510 DOI: 10.1039/D3CP06199J

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