On the formation of CN bonds in Titan’s atmosphere—a unified reaction valley approach study
On the formation of CN bonds in Titan’s atmosphere—a unified reaction valley approach study
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DOI：
10.1007/s00894-021-04917-8
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发表时间：
2021-10
影响因子：
2.2
通讯作者：
M. Freindorf;Nassim Beiranvand;A. A. A. Delgado-A.-A.;Yunwen Tao;E. Kraka
中科院分区：
文献类型：
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作者：
M. Freindorf;Nassim Beiranvand;A. A. A. Delgado-A.-A.;Yunwen Tao;E. Kraka
在这项工作中，我们研究了质子化氰化氢HCNH+和亚甲胺阳离子CH的形成，这两种阳离子都存在于土卫六的高层大气中，它们是由CH4和N+(3P)相互作用的三种不同途径形成的。作为一种机制工具，我们使用了统一反应谷方法(URVA)和局部模式分析(LMA)来评估在这些反应中形成的CN键的强度。我们的URVA研究可以全面概述与发生在三条途径上的八个反应(R1-R8)的具体机制相关的键形成/断裂过程。此外，我们还可以解释CHs的形成以及HCNH+和CHNH的出现。虽然这些反应只涉及较小的分子，包括异构化、氢原子提取和氢分子捕获，但我们发现了一些有趣的特征，如漫游反应R3或在反应R8中H2与HCNH+中的碳原子的初级相互作用，然后其中一个H2氢原子迁移到氮中，这比首先打破HH键更具成本效益；这是催化中经常发现的一个特征。在所有情况下，碳和氮之间的电荷转移可以被确定为CN键形成的驱动力。如LMA所揭示的那样，在反应R1-R8中形成的CN键覆盖了从很弱到很强的宽范围的键强度，其中质子化氰化氢HCNH+中的CN键被确定为本工作所研究的所有分子中最强的。我们的研究表明，URVA和LMA都具有巨大的潜力，可以为这些外星反应提供新的线索，以帮助更好地理解益生菌过程，并为未来涉及复杂星际化学领域的研究制定指导方针。特别是，CN键的形成作为氨基酸外星形成的前驱将是未来研究的重点。通过反应路径曲率可视化土卫六大气中CN键的形成
In this work, we investigated the formation of protonated hydrogen cyanide HCNH+and methylene amine cation CH(both identified in Titan’s upper atmosphere) from three different pathways which stem from the interaction between CH4and N+(3P). As a mechanistic tool, we used the Unified Reaction Valley Approach (URVA) complemented with the Local Mode Analysis (LMA) assessing the strength of the CN bonds formed in these reactions. Our URVA studies could provide a comprehensive overview on bond formation/cleavage processes relevant to the specific mechanism of eight reactionsR1–R8that occur across the three pathways. In addition, we could explain the formation of CHand the appearance of HCNH+and CHNHalong these paths. Although only smaller molecules are involved in these reactions including isomerization, hydrogen atom abstraction, and hydrogen molecule capture, we found a number of interesting features, such asroamingin reactionR3or the primary interaction of H2with the carbon atom in HCNH+in reactionR8followed by migration of one of the H2hydrogen atoms to the nitrogen which is more cost effective than breaking the HH bond first; a feature often found in catalysis. In all cases, charge transfer between carbon and nitrogen could be identified as a driving force for the CN bond formation. As revealed by LMA, the CN bonds formed in reactionsR1–R8cover a broad bond strength range from very weak to very strong, with the CN bond in protonated hydrogen cyanide HCNH+identified as the strongest of all molecules investigated in this work. Our study demonstrates the large potential of both URVA and LMA to shed new light into these extraterrestrial reactions to help better understand prebiotic processes as well as develop guidelines for future investigations involving areas of complex interstellar chemistry. In particular, the formation of CN bonds as a precursor to the extraterrestrial formation of amino acids will be the focus of future investigations.Formation of CN bonds in Titan’s atmosphere visualized via the reaction path curvature