论文标题
通过与星际H2O ICE的CCH反应对乙醇的非能形成。一项计算化学研究
Non-Energetic Formation of Ethanol via CCH Reaction with Interstellar H2O Ices. A Computational Chemistry Study
论文作者
论文摘要
乙醇（$ _3 $ ch $ _2 $ OH）是一个相对常见的分子，通常在恒星形成区域中发现。最近的研究表明，它可能是几个所谓的星际复合有机分子（ICOM）的父分子。然而，该物种的地层途径仍在争论中。在目前的工作中，我们通过CCH与属于冰的一个H $ _2 $ o分子的反应来研究乙醇的形成，作为测试案例，以研究基于“自由基 +冰成分”方案的化学反应的可行性，作为IComs的替代机制，用于ICOM的替代机制，超出了通常的自由基激发式的替补。这是通过DFT计算来完成的，该计算采用了两个和33个水分子作为冰模型的簇。结果表明，ch $ _3 $ ch $ _2 $ oh可以通过这种建议的反应机制形成。 CCH与H $ _2 $ O在水冰簇上的反应可能是无障碍的（借助充当质子转移助理的边界冰冰分子的帮助），导致乙烯基醇前体形成（H $ _2 $ CCOH和CHCHOH）。随后的乙烯基醇产生乙醇的氢化是唯一显示低活化能屏障的步骤。我们最终讨论了这些发现的天体物理含义。
Ethanol (CH$_3$CH$_2$OH) is a relatively common molecule, often found in star forming regions. Recent studies suggest that it could be a parent molecule of several so-called interstellar complex organic molecules (iCOMs). Yet, the formation route of this species remains debated. In the present work, we study the formation of ethanol through the reaction of CCH with one H$_2$O molecule belonging to the ice, as a test case to investigate the viability of chemical reactions based on a "radical + ice component" scheme as an alternative mechanism for the synthesis of iCOMs, beyond the usual radical-radical coupling. This has been done by means of DFT calculations adopting two clusters of 18 and 33 water molecules as ice models. Results indicate that CH$_3$CH$_2$OH can potentially be formed by this proposed reaction mechanism. The reaction of CCH with H$_2$O on the water ice clusters can be barrierless (thanks to the help of boundary icy water molecules acting as proton transfer assistants) leading to the formation of vinyl alcohol precursors (H$_2$CCOH and CHCHOH). Subsequent hydrogenation of vinyl alcohol yielding ethanol is the only step presenting a low activation energy barrier. We finally discuss the astrophysical implications of these findings.
