Cyclopropenone, c-H₂C₃O, has been detected with the 100 m Greenbank telescope toward Sgr B2(N) – largely in absorption:
J. M. Hollis, A. J. Remijan, P. R. Jewell, and F. J. Lovas,
Cyclopropenone (c-H₂C₃O) a new Interstellar Ring Molecule
Astrophys. J. 642, 933–939 (2006).
The molecule was detected in the six lower energy a-type transitions between 8 and 45 GHz. It was not seen in two higher energy transitions. This and the appearance largely in absorption suggests the molecule to be present in the colder and less dense envelope of Sgr B2(N). The molecule can be viewed as a derivative of the ubiquitous, small aromatic cyclopropenylidene, c-C₃H₂.

J.-C. Loison, M. Agúndez, N. Marcelino, V. Wakelam, K. M. Hickson, J. Cernicharo, M. Gerin, E. Roueff, and M. Guélin
reported on
The interstellar chemistry of H₂C₃O isomers
Mon. Not. R. Astron. Soc. 456, 4101–4110 (2016).
The molecule was detected in the 7_1,6 – 6_1,5 transition near 103.1 GHz toward four of seven dark clouds employing the IRAM 30 m telescope. The four sources are TMC-1, B1-b, L483, and Lupus-1A.

In their work on the
Discovery of Linear Propadienone — Study of the Chemistry of Linear and Cyclic H2C3O and H2C3S in TMC-1
Astron. Astrophys. 705, Art. No. A206 (2026),
G. Esplugues, J. C. Loison, M. Agúndez, G. Molpeceres, N. Marcelino, B. Tercero, and J. Cernicharo
also identify isotopic species of cyclopropenone. Two a-type transitions were detected for the C₂ (ethene-type) position, c-H₂¹³CCCO, yielding a c-H₂C₃O to c-H₂¹³CCCO of 23 ± 9 and a ¹²C to ¹³C ratio of 46 ± 18 because of the two equivalent C₂ positions. Only one a-type transition had enough intensity in the case of the carbonyl C (C₁), making the identification somewhat tentative. The ¹²C to ¹³C ratio is about 57. c-HDC₃O was also identified with a H to D ratio of 24 ± 10 because of the two equivalent H positions.

Contributor(s): H. S. P. Müller; 02, 2006; 02, 2016