{"title":"Theoretical Insights into a Novel Ion–Ion Reaction of Methane in the Initial Stages of Hydrocarbon Growth in Space","authors":"Toshiaki Matsubara*, ","doi":"10.1021/acsearthspacechem.4c0024210.1021/acsearthspacechem.4c00242","DOIUrl":null,"url":null,"abstract":"<p >In this article, we examine the reactions between methane molecules as a starting point for hydrocarbon growth in space and assess the effectiveness of the ion–ion reaction between CH<sub>4</sub><sup>+</sup> and CH<sub>4</sub><sup>+</sup> using quantum mechanical and molecular dynamics methods. We modeled the reaction starting from the dicationically ionized [CH<sub>4</sub>···CH<sub>4</sub>]<sup>2+</sup> cluster. Initially, attractive interactions occur between the facing C–H bonds of the tetrahedral structures, which are electron-deficient. As the structure transitions to a trigonal pyramid, a bond begins to form between two carbon atoms with unpaired electrons, resulting in a metastable configuration due to the balance between Coulombic repulsion and attractive forces. The stabilization energy for C–C bond formation was 176.8 kcal/mol, with a bond formation efficiency of 32.6%, and the corresponding rate coefficient was 1.394 × 10<sup>–2</sup> fs<sup>–1</sup>. This stabilization by C–C bond formation generates kinetic energy, and if sufficient energy is redistributed to the vibrational mode of the reaction, the reaction can proceed. Reactions involving C–C bond formation produced precursors of ethane, ethylene, and acetylene, such as C<sub>2</sub>H<sub>6</sub><sup>2+</sup>, C<sub>2</sub>H<sub>5</sub><sup>+</sup>, C<sub>2</sub>H<sub>4</sub><sup>+</sup>, and C<sub>2</sub>H<sub>3</sub><sup>+</sup>, as well as CH<sub>3</sub><sup>+</sup>, a key species in ion–molecule reactions in space. Even without C–C bond formation, a significant amount of CH<sub>3</sub><sup>+</sup> was produced. Our findings underscore the importance of exploring novel ion–ion reactions to deepen our understanding of molecular growth in space.</p>","PeriodicalId":15,"journal":{"name":"ACS Earth and Space Chemistry","volume":"8 12","pages":"2557–2573 2557–2573"},"PeriodicalIF":2.9000,"publicationDate":"2024-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"ACS Earth and Space Chemistry","FirstCategoryId":"92","ListUrlMain":"https://pubs.acs.org/doi/10.1021/acsearthspacechem.4c00242","RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"CHEMISTRY, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
In this article, we examine the reactions between methane molecules as a starting point for hydrocarbon growth in space and assess the effectiveness of the ion–ion reaction between CH4+ and CH4+ using quantum mechanical and molecular dynamics methods. We modeled the reaction starting from the dicationically ionized [CH4···CH4]2+ cluster. Initially, attractive interactions occur between the facing C–H bonds of the tetrahedral structures, which are electron-deficient. As the structure transitions to a trigonal pyramid, a bond begins to form between two carbon atoms with unpaired electrons, resulting in a metastable configuration due to the balance between Coulombic repulsion and attractive forces. The stabilization energy for C–C bond formation was 176.8 kcal/mol, with a bond formation efficiency of 32.6%, and the corresponding rate coefficient was 1.394 × 10–2 fs–1. This stabilization by C–C bond formation generates kinetic energy, and if sufficient energy is redistributed to the vibrational mode of the reaction, the reaction can proceed. Reactions involving C–C bond formation produced precursors of ethane, ethylene, and acetylene, such as C2H62+, C2H5+, C2H4+, and C2H3+, as well as CH3+, a key species in ion–molecule reactions in space. Even without C–C bond formation, a significant amount of CH3+ was produced. Our findings underscore the importance of exploring novel ion–ion reactions to deepen our understanding of molecular growth in space.
期刊介绍:
The scope of ACS Earth and Space Chemistry includes the application of analytical, experimental and theoretical chemistry to investigate research questions relevant to the Earth and Space. The journal encompasses the highly interdisciplinary nature of research in this area, while emphasizing chemistry and chemical research tools as the unifying theme. The journal publishes broadly in the domains of high- and low-temperature geochemistry, atmospheric chemistry, marine chemistry, planetary chemistry, astrochemistry, and analytical geochemistry. ACS Earth and Space Chemistry publishes Articles, Letters, Reviews, and Features to provide flexible formats to readily communicate all aspects of research in these fields.