Butatrienylidene is a higher energy isomer of diacetylene.
J. Cernicharo, C. A. Gottlieb, M Guélin, T. C. Killian, G. Paubert, P. Thaddeus, and J. M. Vrtilek,
reported on the
Astronomical Detection of H2CCCC,
Astrophys. J. 368, L43L45 (1991)
The molecule was detectedin the circumstellar envelope of CW Leonis, also known as IRC +10216 using the IRAM 30 m telescope. 10 transitions with 9 ≤ J' ≤ 16 were sought, and 8 were detected, two of them partially blended. Six transitions had Ka = 1 (ortho) and two had Ka = 0 (para).
The Molecule was also deteceted in the dark cloud TMC-1 by
K. Kawaguchi, N. Kaifu, M. Ohishi, S.-I. Ishikawa, Y. Hirahara, S. Yamamoto, S. Saito, S. Takano, A. Murakami, J. M. Vrtilek, C. A. Gottlieb, P. Thaddeus, and W. M. Irvine,
Observations of Cumulene Carbenes, H2CCCC and H2CCC, in TMC-1,
Publs. Astron. Soc. Japan 43, 607619 (1991)
N. Sakai, T. Sakai, T. Hirota, and S. Yamamoto,
Deuterated Molecules in Warm Carbon Chain Chemsitry: The L1527 Case,
Astrophys. J. 702, 10251035 (2009)
The 50,5 40,4 transition of l-C4HD near 42.4 GHz was detected with the Nobeyama 45 m telescope in emission.