Bridging the gap: viable reaction pathways from tetrahedrane to benzyne.

The addition of sp-carbon-containing molecules to polycyclic sp tetrahedrane (-CH) results in the formation of both -benzyne (-CH) and benzene (-CH). Since both -CH and -CH 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 -CH, benzvalyne, and vinylidene (:CCH). Addition of diatomic carbon (C), the ethynyl radical (CH), vinylidene, and acetylene (HCCH) to -CH is undertaken in individual pathways through high-level quantum chemical computations at the CCSD(T)-F12b/cc-pVTZ-F12 level of theory. The resulting C addition pathway proceeds barrierlessly through benzvalyne as an intermediate and reaches a true minimum at -CH, but no leaving groups are produced which is required to dissipate excess energy within an interstellar chemical scheme. Similarly, the CH addition to -CH 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CH and :CCH addition pathways follow through both benzvalene and benzvalyne in order to reach -CH (benzene) and -CH (-benzyne) as well as H as the required leaving group. Although there is a barrier to the HCCH addition, the :CCH addition presents the contrary with only submerged barriers. These proposed mechanisms provide alternative possibilities for the formation of complex organic molecules in space.