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A quantum chemical study on the formation of ethanimine (CH3CHNH) in the interstellar ice

Authors
  • Singh, Keshav Kumar1
  • Shivani,1, 2
  • Tandan, Poonam1
  • Misra, Alka2
  • 1 University of Lucknow, Department of Physics, Lucknow, India , Lucknow (India)
  • 2 University of Lucknow, Department of Mathematics & Astronomy, Lucknow, India , Lucknow (India)
Type
Published Article
Journal
Astrophysics and Space Science
Publisher
Springer Netherlands
Publication Date
Sep 24, 2018
Volume
363
Issue
10
Identifiers
DOI: 10.1007/s10509-018-3399-6
Source
Springer Nature
Keywords
License
Yellow

Abstract

Ethanimine (CH3CHNH) is an important prebiotic molecule since it is a precursor of amino acid α\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$\alpha $\end{document}-alanine in Strecker synthesis. Two isomers (E and Z) of ethanimine were detected in the molecular cloud Sagittarius B2 north during GBT-PRIMOS survey. A possible radical-molecule reaction pathway has been proposed for the formation of ethanimine in the interstellar medium (ISM) from some previously detected interstellar molecules like methylene (both triplet CH2 (3B1) and singlet CH2 (1A1)) and methyenimine (CH2NH). The mechanism has been studied in the gas phase and in water ice with the help of density functional theory at B2PLYPD/6-311++G (2d, p) level of theory. It is observed that E-ethanimine forms efficiently in gas phase but ice reactions are favorable only in the hot core of molecular clouds. Same is true for the formation of Z-ethanimine which forms only at the surface of water cluster as the height of entrance barrier for formation of Z-ethanimine is similar to that of E-ethanimine. Isomerization from E to Z form is also studied and found to be forbidden due to large entrance barrier. Out of the two reaction system CH2 (3B1) + CH2NH and CH2 (1A1) + CH2NH, later is more favorable then the former one due to the small entrance barrier. Still, much of the detected abundance of ethanimine comes from the reaction of CH2 (3B1) with CH2NH as since CH2 (1A1) has very low abundance compared to the CH2 (3B1) in ISM. The proposed pathway seems to be a promising candidate for the ethanimine formation in ISM.

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