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| molecules:ism:proh [2022/06/28 16:53] – mueller | molecules:ism:proh [2022/08/04 11:53] (current) – mueller |
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| ===== Propanol Isomers, C3H7OH, in Space ===== | ===== Propanol Isomers, C3H7OH, in Space ===== |
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| There are two isomers of propanol, the straight-chain //normal//- or just //n//-propanol, also known as 1-propanol, and the branched //iso//- or just //i//-propanol, also known as 2-propanol. There is another structural isomer, [[molecules:ism:eme|ethyl methyl ether]], also known as methoxyethane (CH<sub>3</sub>OC<sub>2</sub>H<sub>5</sub>), whose detection was already reported.\\ | There are two isomers of propanol, the straight-chain //normal//- or just //n//-propanol, also known as 1-propanol, and the branched //iso//- or just //i//-propanol, also known as 2-propanol. There is another structural isomer, **[[molecules:ism:eme|ethyl methyl ether]]**, also known as methoxyethane (CH<sub>3</sub>OC<sub>2</sub>H<sub>5</sub>), whose detection was already reported.\\ |
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| To make matters more complicated, //n//-propanol exists in five conformers which are descrobed by the orientation of the terminal CH<sub>3</sub> group and by the OH group. The //anti// conformation refers to a dihedral angle of 180<sup>o</sup> with respect to the CCO plane, whereas the //gauche// conformations refer to a dihedral angle of ±60<sup>o</sup>. //A// and //G// refer to the orientations of the methyl group, //a//, //g//, and //g'// to that of the OH group. //Ga// is the lowest energy conformer, //Gg// and //Gg'// are higher in energy, and the energy differences are known very well from rotational spectroscopy. //Aa// is probably between //Ga// and //Gg// while //Ag// may be highest in energy. Tunneling within //Ag// leads to //Ag//<sup>+</sup> and //Ag//<sup>−</sup> substates which are separated in energy by roughly 100 GHz.\\ | To make matters more complicated, //n//-propanol exists in five conformers which are descrobed by the orientation of the terminal CH<sub>3</sub> group and by the OH group. The //anti// conformation refers to a dihedral angle of 180<sup>o</sup> with respect to the CCO plane, whereas the //gauche// conformations refer to a dihedral angle of ±60<sup>o</sup>. //A// and //G// refer to the orientations of the methyl group, //a//, //g//, and //g'// to that of the OH group. //Ga// is the lowest energy conformer, //Gg// and //Gg'// are higher in energy, and the energy differences are known very well from rotational spectroscopy. //Aa// is probably between //Ga// and //Gg// while //Ag// may be highest in energy. Tunneling within //Ag// leads to //Ag//<sup>+</sup> and //Ag//<sup>−</sup> substates which are separated in energy by roughly 100 GHz.\\ |
| reported on\\ | reported on\\ |
| **[[https://doi.org/10.1051/0004-6361/202142699|Precursors of Fatty Alcohols in the ISM: Discovery of //n//-Propanol]]**\\ | **[[https://doi.org/10.1051/0004-6361/202142699|Precursors of Fatty Alcohols in the ISM: Discovery of //n//-Propanol]]**\\ |
| //Astron. Astrophys.//, (2022), in press.\\ | //Astron. Astrophys.// **663** (2022), Art. No. A181.\\ |
| Transitions of the //Ga// and //Aa// conformers of 1-propanol were observed in the course of a molecular line survey of the quiescent giant molecular cloud G+0.693−0.027, about 1' north-east of Sagittarius (Sgr) B2(N) carried out with the Yebes 40 m dish at 7 mm and with the IRAM 30 m dish at 3, 2, and 1 mm. The identified transitions cover the 2 to 7 mm regions 2 ≤ //J// ≤ 11 and //K<sub>a</sub>// ≤ 6 for //Ga// and 2 ≤ //J// ≤ 12 and //K<sub>a</sub>// ≤ 3 for //Aa//. The number of clean, slightly or partly blended transitions is sufficiently large for both conformers together and for //Ga// alone. The excitation temperature is about 13 K. //n//-Propanol is about a factor of 15 less abundant than ethanol which, in turn, is about a factor of 25 less abundant than methanol.\\ | Transitions of the //Ga// and //Aa// conformers of 1-propanol were observed in the course of molecular line surveys of the quiescent giant molecular cloud G+0.693−0.027, about 1' north-east of Sagittarius (Sgr) B2(N) carried out with the Yebes 40 m dish at 7 mm and with the IRAM 30 m dish at 3, 2, and 1 mm. The identified transitions cover the 2 to 7 mm regions 2 ≤ //J// ≤ 11 and //K<sub>a</sub>// ≤ 6 for //Ga// and 2 ≤ //J// ≤ 12 and //K<sub>a</sub>// ≤ 3 for //Aa//. The number of clean, slightly or partly blended transitions is sufficiently large for both conformers together and for //Ga// alone. The excitation temperature is about 13 K. //n//-Propanol is about a factor of 15 less abundant than ethanol which, in turn, is about a factor of 25 less abundant than methanol.\\ |
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| The authors also reported the first detection of //n//-propanol in a star-forming region. Interestingly, eight transitions of the higher lying //Gg'// conformer with 8 ≤ //J// ≤ 12 and //K<sub>a</sub>// ≤ 4 and five transitions of the higher lying //Ag// conformer with 12 ≤ //J// ≤ 15 and //K<sub>a</sub>// ≤ 6 were detected. Transitions of the lower lying conformers were also present, but all were blended more or less severely. Rotational temperatures of 135 K were inferred. The iso to normal ratio is about 0.6, fairly similar to the 0.4 ratio in the case of the two propyl cyanide isomers. In addition, //n//-propanol is about a factor of 18 less abundant than ethanol which, in turn, is about a factor of 19 less abundant than methanol.\\ | The authors also reported the first detection of //n//-propanol in a star-forming region. Interestingly, eight transitions of the higher lying //Gg'// conformer with 8 ≤ //J// ≤ 12 and //K<sub>a</sub>// ≤ 4 and five transitions of the higher lying //Ag// conformer with 12 ≤ //J// ≤ 15 and //K<sub>a</sub>// ≤ 6 were detected. Transitions of the lower lying conformers were also present, but all were blended more or less severely. Rotational temperatures of 135 K were inferred. The iso to normal ratio is about 0.6, fairly similar to the 0.4 ratio in the case of the two propyl cyanide isomers. In addition, //n//-propanol is about a factor of 18 less abundant than ethanol which, in turn, is about a factor of 19 less abundant than methanol.\\ |
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| The Max-Planck-Institut für Radioastronomie issued a press release in **[[https://www.mpifr-bonn.mpg.de/pressreleases/2022/10?c=9060|English]]** and in [[https://www.mpifr-bonn.mpg.de/pressemeldungen/2022/10?c=8727|German]]** | The Max-Planck-Institut für Radioastronomie issued a press release in **[[https://www.mpifr-bonn.mpg.de/pressreleases/2022/10?c=9060|English]]** and in **[[https://www.mpifr-bonn.mpg.de/pressemeldungen/2022/10?c=8727|German]]**. Similar press releases were issued by the **[[https://www.mpg.de/18884791/sanitizer-in-the-galactic-centre-region|Max Planck Society]]** and by the **[[https://portal.uni-koeln.de/en/universitaet/aktuell/press-releases/single-news/a-sanitizer-in-the-galactic-centre-region|Universität zu Köln]]**. |
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