星际烯醇化-乙醛 (CH3CHO) 和乙烯醇 (H2CCH(OH)) 作为案例研究,ChemPhysChem

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星际烯醇化-乙醛 (CH3CHO) 和乙烯醇 (H2CCH(OH)) 作为案例研究
ChemPhysChem ( IF 2.3 ) Pub Date : 2021-04-28 , DOI: 10.1002/cphc.202100111
N Fabian Kleimeier ₁ , Ralf I Kaiser ₁

Affiliation

由于冷分子云中的独特条件，烯醇（醛和酮的热力学稳定性较差的互变异构体）不会在气相中发生互变异构化为更稳定的互变异构体，因为它们在低温下无法克服互变异构障碍。星际模拟冰的实验室研究表明，在过去几年中，在天体化学相关的冰混合物中形成了几个酮-烯醇互变异构体对。然而，到目前为止，只有一种乙醛-乙烯醇在深空被探测到。由于它们与亲电子试剂的反应性，烯醇可以在我们理解星际介质、彗星和陨石中的分子复杂性方面发挥关键作用。为了通过与银河宇宙射线 (GCR) 的相互作用研究星际冰中醛的烯醇化，我们用高能电子照射乙醛冰，作为在穿透星际冰时在 GCR 轨道中产生的二次电子的代理。结果表明 GCR 可以诱导乙醛的烯醇化，并且分子内和分子间过程是相关的。因此，烯醇在星际介质中应该无处不在，可以使用射电望远镜（如 ALMA）进行搜索。一旦检测到烯醇并确定丰度，它们就可以作为星际冰中非平衡化学的示踪剂，从而最终限制星际冰深处的基本反应机制。结果表明 GCR 可以诱导乙醛的烯醇化，并且分子内和分子间过程是相关的。因此，烯醇在星际介质中应该无处不在，可以使用射电望远镜（如 ALMA）进行搜索。一旦检测到烯醇并确定丰度，它们就可以作为星际冰中非平衡化学的示踪剂，从而最终限制星际冰深处的基本反应机制。结果表明 GCR 可以诱导乙醛的烯醇化，并且分子内和分子间过程是相关的。因此，烯醇在星际介质中应该无处不在，可以使用射电望远镜（如 ALMA）进行搜索。一旦检测到烯醇并确定丰度，它们就可以作为星际冰中非平衡化学的示踪剂，从而最终限制星际冰深处的基本反应机制。

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Interstellar Enolization-Acetaldehyde (CH3CHO) and Vinyl Alcohol (H2CCH(OH)) as a Case Study

Owing to the unique conditions in cold molecular clouds, enols—the thermodynamically less stable tautomers of aldehydes and ketones—do not undergo tautomerization to their more stable tautomers in the gas phase because they cannot overcome tautomerization barriers at the low temperatures. Laboratory studies of interstellar analog ices have demonstrated the formation of several keto–enol tautomer pairs in astrochemically relevant ice mixtures over the last years. However, so far only one of them, acetaldehyde−vinyl alcohol, has been detected in deep space. Due to their reactivity with electrophiles, enols can play a crucial role in our understanding of the molecular complexity in the interstellar medium and in comets and meteorites. To study the enolization of aldehydes in interstellar ices by interaction with galactic cosmic rays (GCRs), we irradiated acetaldehyde ices with energetic electrons as proxies of secondary electrons generated in the track of GCRs while penetrating interstellar ices. The results indicate that GCRs can induce enolization of acetaldehyde and that intra- as well as intermolecular processes are relevant. Therefore, enols should be ubiquitous in the interstellar medium and could be searched for using radio telescopes such as ALMA. Once enols are detected and abundances are established, they can serve as tracers for the non-equilibrium chemistry in interstellar ices thus eventually constraining fundamental reaction mechanisms deep inside interstellar ices.

更新日期：2021-06-18

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