I. R. Cooke, C. Xue, P. B. Changala, H. T. Shay, A. N. Byrne, Q. Y. Tang, Z. T. P. Fried, K. L. K. Lee, R. A. Loomis, T.Lamberts, A. Remijan, A. M. Burkhardt, E. Herbst, M. C. McCarthy, and B. A. McGuire
reported on
Detection of Interstellar //E//-1-cyano-1,3-butadiene in GOTHAM Observations of TMC-1
Astrophys. J. 948, Art. No. 133 (2023).
The identification was made by stacking data from the GBT line survey that covers ~24.9 GHZ of the 7.9 to 36.4 GHz region. The E form of 1-cyano-1,3-butadiene is less abundant than the two detected cyanocyclopentadiene isomers by factors of a few, somewhat depending on the sources of the column densities of the cyclic species.

M. Agúndez, C. Cabezas, N. Marcelino, B. Tercero, R. Fuentetaja, P. de Vicente, and J. Cernicharo
cast serious doubt on this detection in their study
A Search for the Three Isomers of Cyano-1,3-butadiene in TMC-1: Implications for Bottom-up Routes Involving 1,3-Butadiene
Astron. Astrophys. 697, Art. No. A82 (2025).
They use their QUIJOTE line survey between 31.0 and 50.3 GHz to search for E-1-, Z-1-, and 2-cyano-1,3-butadiene. None of the isomers was detected. Moreover, the upper limit for the column density of E-1-cyano-1,3-butadiene is a factor of three lower than the one reported in the study above. Therefore, the molecule is considered as undetected for now. An additional outcome of this study is that the role of 1,3-butadiene in the bottom-up formation of PAHs is likely smaller than thought thus far.

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Contributor(s): H. S. P. Müller; 07, 2023; 05, 2025

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