===== On the Detection of Benzonitrile, c-C6H5CN, in the ISM =====

B. A. McGuire, A. M. Burkhardt, S. V. Kalenskii, C. N. Shingledecker, A. J. Remijan, E. Herbst, and M. C. McCarthy\\
reported on the\\
**[[https://doi.org/10.1126/science.aao4890|Detection of the Aromatic Molecule Benzonitrile, //c//-C<sub>6</sub>H<sub>5</sub>CN, in the Interstellar Medium]]**\\
//Science// **359**, 202–205 (2018).\\
The molecule, also known as phenyl cyanide, was detected first by stacking of rotational transitions observed in archival Nobeyama 45 m data. It was the only molecule out of a dozen cyclic molecules searched for that was detected by this method. Subsequently, attempts were made to detect individual transitions with the GBT 100 m telescope by covering a total of 1.875 GHz in the 18 to 23 GHz region. Nine transitions with //J'// = 7 to 9 and //K<sub>a</sub>// =  0 to 2 were detected with modest to fairly good signal-to-noise ratios. Some of these transitions displayed partially resolved <sup>14</sup>N hyperfine structure. The inferred column density is somewhat lower than that of HC<sub>9</sub>N, the largest unambigously detected cyanopolyyne thus far.\\
NRAO issued a [[https://public.nrao.edu/news/2018-gbt-chemistry/|press release]] which was also issued by the CfA.\\
The molecule was the most promising candidate for the detection of a benzene derived aromatic molecule by means of radio astronomy. Was it surprising that it was found in TMC-1 ?\\
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A. M. Burkhardt, R. A. Loomis, C. N. Shingledecker, K. L. K. Lee, A. J. Remijan, M. C. McCarthy, and B. A. McGuire\\
reported on the\\
**[[https://doi.org/10.1038/s41550-020-01253-4|Ubiquitous aromatic carbon chemistry at the earliest stages of star formation]]**\\
//Nat. Astron.// **5**, 181–187 (2021).\\
Benzonitrile was detected by the same method as in the first reference toward four additional dark clouds, Serpens 1A, 1B, 2, and L1521F. The HC<sub>7</sub>N///c//-C<sub>6</sub>H<sub>5</sub>CN ratio was found to be around 5 for the first threre sources and ~17 for L1521F. The last value is very similar to the one in TMC-1 derivewd from the previous entry.\\
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V. M. Rivilla, D. San Andrés, M. Sanz-Novo, L. Colzi, I. Jiménez-Serra, A. López-Gallifa, A. Martínez-Henares, A. Megías, S. Martín, B. Tercero, S. Zeng, J. Loreau, M. Ben Khalifa, M. A. Requena-Torres and P. de Vicente \\
announced\\
**[[https://doi.org/10.1051/0004-6361/202660367|Aromatic Rings in the Central Molecular Zone: Benzonitrile]]**\\
//Astron. Astrophys.// **712**, Art. No. A128 (2026).\\
The molecule was detected in two kinetically warmer, rotationally cold clouds  G+0.693−0.027 and G+0.633−0.0604 close to the Galactic center in the course of molecular line surveys with the Yebes 40 m dish. The HC<sub>7</sub>N///c//-C<sub>6</sub>H<sub>5</sub>CN ratios of ~2.15 and ~2.4 are even lower than the values reported earlier. Additional values of comparison are given from other publications, including a value of ~30 in Lupus-1A.\\
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Contributor(s): H. S. P. Müller; 01, 2018; 04, 2021; 08, 2026

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