The cyanomethyl radical H₂CCN had been identified in spectra recorded toward TMC-1 and Sgr B2 first by
W. M. Irvine, P. Friberg, Å. Hjalmarson, S. Ishikawa, N. Kaifu, K. Kawaguchi, S. C. Madden, H. E. Matthews, M. Ohishi, S. Saito, H. Suzuki, P. Thaddeus, B. E. Turner, S. Yamamoto, L. M. Ziurys,
Identification of the Interstellar Cyanomethyl Radical (CH₂CN) in the Molecular Clouds TMC-1 and Sagittarius B2
Astrophys. J. 334, L107–L111 (1988).
Some of these lines have been observed before and attributed to one unknown insterstellar molecule
S. E. Cummins, R. A. Linke, and P. Thaddeus,
A survey of the millimeter-wave spectrum of Sagittarius B2
Astrophys. J. 576, 819–878 (1986).

Quite recently, H₂CCN was among several molecules detected with the IRAM 30 m telecope in the circumstellar envelope of the carbon-rich AGB star CW Leo, aka IRC +10216:
M. Agúndez, J. P. Fonfría Expósito, J. Cernicharo, J. R. Pardo and M. Guélin,
Detection of Circumstellar CH₂CHCN, CH₂CN, CH₃CCH, and H₂CS
Astron. Astrophys. 479, 493–501 (2008).

C. Cabezas, Y. Endo, E. Roueff, N. Marcelino, M. Agúndez, B. Tercero, and J. Cernicharo
reported on the
Space and laboratory observation of the deuterated cyanomethyl radical HDCCN
Astron. Astrophys. 646, Art. No. L1 (2021).
The 2₀₂ − 1₀₁ transition near 37.49 GHz with fine and hyperfine structure splitting was detected toward TMC-1 using the Yebes 40 m radio telescope in the course of a molecular line survey. The derived H₂CCN to HDCCN ratio is 20 ± 4, i.e., ~40 per H atom, quite normal for TMC-1.

Contributor(s): H. S. P. Müller; 12, 2003; 07, 2011; 02, 2021