===== Detection Propene in the ISM =====

The propene molecule C<sub>3</sub>H<sub>6</sub>, aka propylene, has been identified in spectra recorded toward TMC-1 by\\
N. Marcelino, J. Cernicharo, M. Agúndez, E. Roueff, M. Gerin, J. Martín-Pintado, R. Mauersberger, and C. Thum,\\
**[[https://doi.org/10.1086/521398|Discovery of Interstellar Propylene (CH<sub>2</sub>CHCH<sub>3</sub>): Missing Links in Interstellar Gas-Phase Chemistry]]**\\
//Astrophys. J.// **665**, L127–L130 (2007).\\
Six rotational transitions each split into two //A// and //E// components due to the CH<sub>3</sub> interal rotation were observed plus one //A// component for which the //E// line is overlapped. The observation of this molecule in TMC-1 was rather surprising because apparently noone in the community considered such an almost saturated molecule to be likely in this source – especially because of thus far missing routes to this molecule. Even more remarkable is the detection because of the high abundance; a column density of 4 × 10<sup>13</sup> cm<sup>-2</sup> was derived; comparable to the abundance of //c//-C<sub>3</sub>H<sub>2</sub>.\\
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M. Agúndez, J. Cernicharo, and M. Guélin\\
reported the detection of propene by the two methyl internal rotor states of the 5<sub>05</sub> – 4<sub>04</sub> transition near 86.65 GHz with the IRAM 30 m telescope toward 4 out of 5 dark clouds (Lupus-1a, L1495B, L1521F, and Serpens South 1a) in their report on\\
**[[https://doi.org/10.1051/0004-6361/201526317|Discovery of Interstellar Ketenyl (HCCO), a Surprisingly Abundant Radical]]**\\
//Astron. Astrophys.// **577**, Art. No. L5 (2015).\\
Emission of up to three more rotational transitions were also detected.\\
\\

S. Manigand, A. Coutens, J.-C. Loison, V. Wakelam, H. Calcutt, H. S. P. Müller, J. K. Jørgensen, V. Taquet, S. F. Wampfler, T. L. Bourke, B. M. Kulterer, E. F. van Dishoeck, M. N. Drozdovskaya, and N. F. W. Ligterink\\
reported on\\
**[[https://doi.org/10.1051/0004-6361/202038113|The ALMA-PILS Survey: First Detection of the Unsaturated Three-carbon Molecules Propenal (C<sub>2</sub>H<sub>3</sub>CHO) and Propylene (C<sub>3</sub>H<sub>6</sub>) towards the Low-mass Protostar IRAS 16293–2422 B]]**\\
//Astron. Astrophys.// **645**, Art. No. A53 (2021).\\
This is the first account on luke-warm (~ 75 K) propene in the ISM and on the detection of propene around a low-mass protostar. The Protostellar Interferometric Line Survey (PILS) was carried out with ALMA in its Band 7 (329 – 363 GHz) with additional observations in Band 6. A total of 17 different unblended (with respect to a different molecule) lines were identified.


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Contributor(s): H. S. P. Müller; 08, 2007; 05, 2015; 02, 2021


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