===== The Detection of Cyanomethanimines in the ISM =====

C-cyanomethanimine, HNCHCN, is a slightly unsaturated sibling of [[molecules:ism:aan|aminoacetonitrile]], H<sub>2</sub>NCH<sub>2</sub>CN. It has been identified recently by\\
D. P. Zaleski, N. A. Seifert, A. L. Steber, M. T. Muckle, R. A. Loomis, J. F. Corby, O. Martinez, Jr., K. N. Crabtree, P. R. Jewell, J. M. Hollis, F. J. Lovas, D. Vasquez, J Nyiramahirw, N. Sciortino, K. Johnson, M. C. McCarthy, A. J. Remijan, and B. H. Pate,\\
**[[https://doi.org/10.1088/2041-8205/765/1/L10|Detection of //E//-Cyanomethanimine toward Sagittarius B2(N) in the Green Bank Telescope PRIMOS Survey]]**\\
//Astrophys. J// **765**, Art. No. 10 (2013).\\
8 rotational transitions were detected for the higher energy //E//-conformer and none for the lower energy //Z//-conformer. The non-observation of the //Z//-conformer was attributed to the much smaller dipole moment components. The transitions had //J// < 5 and //K<sub>a</sub>// < 1, occured between 9 and 48 GHz and were all seen in absorption. Some transitions displayed <sup>14</sup>N hyperfine splitting. The lines were detected in the two well known velocity components 64 km/s and 82 km/s, though (partial) overlap occured for the latter in some lines. A rotational temperature of about 8 K was derived.\\
These, as well as other observations of fairly complex molecules toward Sgr B2(N) at apperently low rotational temperatures, may be related to findings by\\
M. A. Requena-Torres, J. Martín-Pintado, A. Rodríguez-Franco, S. Martín, N. J. Rodríguez-Fernández, and P. de Vicente,\\
**[[https://doi.org/10.1051/0004-6361:20065190|Organic Molecules in the Galactic Center – Hot Core Chemistry without Hot Cores]]**\\
//Astron. Astrophys.// **455**, 971–985 (2006);\\
and by\\
M. A. Requena-Torres, J. Martín-Pintado, S. Martín, and M. R. Morris,\\
**[[https://doi.org/10.1086/523627|The Galactic Center: The Largest Oxygen-bearing Organic Molecule Repository]]**\\
//Astrophys. J.// **672**, 352–360 (2008).\\
\\

V. M. Rivilla, J. Martín-Pintado, I. Jiménez-Serra, S. Zeng, S. Martín, J. Armijos-Abendañdo, M. A. Requena-Torres, R. Aladro, and D. Riquelme\\
reported on\\
**[[https://doi.org/10.1093/mnrasl/sly228|Abundant Z-cyanomethanimine in the Interstellar Medium: Paving the Way to the Synthesis of Adenine]]**\\
//Mon. Not. R. Soc. Astron.// **483**, L114–L119 (2019).\\
The results were obtained in the course of a line survey of the Galactic center source G 0.693–0.03 at 3 mm using the IRAM 30 m dish; additional observation around 1.3 cm were carried out with the GBT 100 m dish. The //E//-conformer was also identified. The Z/E ratio of about six indicated thermal equilibrium at the kinetic temperature of the cloud. The excitation temperature, in contrast, is rather cold, about 8 K.\\
\\

D. San Andrés, V. M. Rivilla, L. Colzi, I. Jiménez-Serra, J. Martín-Pintado, A. Megías, Á. López-Gallifa, A. Martínez-Henares, S. Massalkhi, S. Zeng, M. Sanz-Novo, B. Tercero, P. de Vicente, S. Martín, M. A. Requena Torres, G. Molpeceres, and J. García de la Concepción\\
described the\\
**[[https://doi.org/10.3847/1538-4357/ad3af3|First Detection in Space of the High-energy Isomer of Cyanomethanimine: H<sub>2</sub>CNCN]]**\\
//Astrophys. J.// **967**, Art. No 39 (2024).\\
The results were obtained in the course of line surveys of the Galactic center source G 0.693–0.03 using the Yebes 40 m and IRAM 30 m telescopes. 14 //a//-type transitions with 2 ≤ //J// ≤ 10, //K<sub>a</sub>// ≤ 2 were identified between 31 and 107 GHz. Six of these transitions were unblended or only slightly blended. A non-thermal C-/N-cyanomethanimine ratio of ~32 was derived, while the //Z//-///E//-cyanomethanimine ratio of ~4.5 was deemed to be thermal, as may be expected for a pair of conformers. In contrast, N-cyanomethanimine is an isomer of C-cyanomethanimine, meaning, it requires the formal breaking of at least one bond for interconversion.\\
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Contributor(s): H. S. P. Müller; 02, 2013; 01, 2019; 05, 2024

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