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Isomers in Interstellar Environments. I. The Case of Z- and E-cyanomethanimine.
- Source :
- Astrophysical Journal; Aug2020, Vol. 897 Issue 2, p1-11, 11p
- Publication Year :
- 2020
-
Abstract
- In this work, we present the results of our investigation into the chemistry of Z- and E-cyanomethanimine (HNCHCN), both of which are possible precursors to the nucleobase adenine. Ab initio quantum chemical calculations for a number of reactions with atomic hydrogen were carried out. We find that the reaction H + Z/E-HNCHCN leading both to H-addition as well as H<subscript>2</subscript>-abstraction proceed via similar short-range barriers with bimolecular rate coefficients on the order of ∼10<superscript>−17</superscript> cm<superscript>3</superscript> s<superscript>−1</superscript>. These results were then incorporated into astrochemical models and used in simulations of the giant molecular cloud G+0.693. The calculated abundances obtained from these models were compared with previous observational data and found to be in good agreement, with a predicted [Z/E] ratio of ∼3—somewhat smaller than the previously derived value of 6.1 ± 2.4. We find that the [Z/E] ratio in our simulations is due mostly to ion-molecule destruction rates driven by the different permanent dipoles of the two conformers. Based on these results, we propose a general rule-of-thumb for estimating the abundances of isomers in interstellar environments, which we call the "relative dipole principle." [ABSTRACT FROM AUTHOR]
- Subjects :
- MOLECULAR clouds
ISOMERS
NUCLEAR reactions
ATOMIC hydrogen
ATOMIC number
Subjects
Details
- Language :
- English
- ISSN :
- 0004637X
- Volume :
- 897
- Issue :
- 2
- Database :
- Complementary Index
- Journal :
- Astrophysical Journal
- Publication Type :
- Academic Journal
- Accession number :
- 144876067
- Full Text :
- https://doi.org/10.3847/1538-4357/ab94b5