After the report of the tentative detection of ethynylbenzene (C₆H₅CCH) toward TMC-1 by Cernicharo and co-workers in 2021, subsequent analysis of the ongoing QUIJOTE line survey in 2023 by Loru and co-workers confirmed the detection. Part of the effort of the follow-up study by Loru et al. involved experiments that generated 1,2-diethynylbenzene and then determined its rotational constants and other parameters. A search for 1,2-diethynylbenzene in the TMC-1 line survey was unsuccessful. Various neutral-neutral reactions can yield ethynylbenzene: the most dominant one may be C₆H₆ + CCH → C₆H₅CCH + H.

Ethynylbenzene or phenylacetylene is a monocyclic aromatic hydrocarbon. Unlike benzene, it has a dipole moment and can thus be detected via its rotational spectrum. Its dipole moment (0.72 D) is considerably weaker than the dipole moment of cyanobenzene (benzonitrile) (4.7 D), which was detected in 2018. Ethynylbenzene is widely available commerically and is used in organic synthesis. It is also found in Tuber borchii, a variety of truffle.