Propargyl cyanide (HCCCH₂CN) has been detected toward TMC-1, as reported first by McGuire and coworkers in 2020 and confirmed by Marcelino and coworkers in 2021. The first group used the 100m Green Bank Telescope for their observations, while the second group used the Yebes 40m telescope. Hyperfine lines of various rotational transistions were resolved in both sets of observations. A previous search reported in 2006 at lower resolution by Lovas and coworkers toward TMC-1 did not detect propargyl cyanide, but it did detect the cyanoallene isomer (CH₂CCHCN) for the first time as well as confirming the detection of a third isomer, methylcyanoaceylene (CH₃CCCN).

Propargyl cyanide is also known as 3-butynenitrile and is one the dozens of cyanide and isocyanide compounds that have been detected in astrophysical sources. The propargyl radical and Z-propargylimine have been detected, but a radical derived from propargyl cyanide was sought but not detected.