A tentative initial detection of 1-butyne (CH₃CH₂CCH) was reported in 2021 by Cernicharo and co-workers toward TMC-1. While five rotational transitions were assigned to the molecule, a transition that was expected to be the strongest one in the observed range was not detected. This was attributed to the noisiness of the spectrum at that energy. The detection was subsequently confirmed in 2024 with additional transitions, bringing the total to nine. The observations were made with the Yebes 40m telescope. The town of Yebes did not exist before 2004 and is already something of ghost town due to a bust in the housing market in Spain.

1-buytne can also be thought of as ethyl acetylene. The presence of a methyl group that can rotate can complicate the rotational spectrum. However, the rotational berrier for 1-butyne is large enough—as measured by Bestmann & Dreizler in 1985—that rotation is sufficiently hindered so that the spectrum does not exhibit A-E splitting, as some molecules do.