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

The addition of sp-carbon-containing molecules to polycyclic sp 3 tetrahedrane ( c -C 4 H 4 ) results in the formation of both o -benzyne ( c -C 6 H 4 ) and benzene ( c -C 6 H 6 ). Since both c -C 6 H 4 and c -C 6 H 6 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 -C 4 H 4 , benzvalyne, and vinylidene (:CCH 2 ). Addition of diatomic carbon (C 2 ), the ethynyl radical (C 2 H), vinylidene, and acetylene (HCCH) to c -C 4 H 4 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 2 addition pathway proceeds barrierlessly through benzvalyne as an intermediate and reaches a true minimum at c -C 6 H 4 , but no leaving groups are produced which is required to dissipate excess energy within an interstellar chemical scheme. Similarly, the C 2 H addition to c -C 4 H 4 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 2 addition pathways follow through both benzvalene and benzvalyne in order to reach c -C 6 H 6 (benzene) and c -C 6 H 4 ( o -benzyne) as well as H 2 as the required leaving group. Although there is a barrier to the HCCH addition, the :CCH 2 addition presents the contrary with only submerged barriers. These proposed mechanisms provide alternative possibilities for the formation of complex organic molecules in space.