Darla Nagasuneetha, Sitha Sanyasi
Department of Chemical Sciences, APK Campus , University of Johannesburg , P.O. Box 524, Auckland Park, Johannesburg 2006 , South Africa.
J Phys Chem A. 2019 Oct 17;123(41):8921-8931. doi: 10.1021/acs.jpca.9b07255. Epub 2019 Oct 8.
Formamide (NHCHO) is the smallest molecular unit that contains the basic peptide linkage and thus has recently attracted a great amount of interest in the field of astrochemistry. In this work using computational calculations, we have analyzed the three possible reaction paths for the reaction between CO and NH to form formamide in both neutral-neutral and cation-neutral reaction surfaces. All of these three paths strongly favor the path of 1,2-hydrogen migration, which was discounted by previous studies in view of the constraints from steric factor. We have also analyzed the significant role played by prereaction complexes in these three reaction paths. We have proposed that for the neutral-neutral reaction path, formation of formamide in the low temperature interstellar clouds was hypothesized to proceed via hydrogen tunneling assisted by a tunneling ready like state as prereaction complex. On the other hand, for the two cation-neutral reactions, any tunneling cannot facilitate formation of formamide in the interstellar clouds. Rather in one case as all the stationary points are below the reactants, it can facilitate the reaction, whereas in the second case the reaction is only possible if it can get some catalytic assistance.
甲酰胺（NHCHO）是包含基本肽键的最小分子单元，因此最近在天体化学领域引起了极大的关注。在这项使用计算方法的工作中，我们分析了在中性-中性和阳离子-中性反应表面上，CO与NH反应生成甲酰胺的三种可能反应路径。这三条路径都强烈倾向于1,2-氢迁移路径，而先前的研究由于空间因素的限制而忽略了这条路径。我们还分析了预反应复合物在这三条反应路径中所起的重要作用。我们提出，对于中性-中性反应路径，假设在低温星际云中通过像预反应复合物那样的易于隧穿状态辅助的氢隧穿来生成甲酰胺。另一方面，对于两个阳离子-中性反应，任何隧穿都不能促进星际云中甲酰胺的形成。相反，在一种情况下，由于所有驻点都低于反应物，它可以促进反应，而在第二种情况下，只有在获得某种催化作用时反应才可能发生。
