Aromatics and Cyclic Molecules in Molecular Clouds: A New Dimension of Interstellar Organic Chemistry
Aromatics and Cyclic Molecules in Molecular Clouds: A New Dimension of Interstellar Organic Chemistry
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DOI：
10.1021/acs.jpca.1c00129
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发表时间：
2021-03-22
影响因子：
2.9
通讯作者：
McGuire, Brett A.
中科院分区：
文献类型：
--
作者：
McCarthy, Michael C.;McGuire, Brett A.
天体化学是天文学、化学和分子物理学的结合点。在精确的实验室数据的基础上，在星际介质中发现了200多种熟悉和奇异的分子，其中绝大多数是通过其独特的旋转指纹。尽管有这么多的工作，在无线电波段上还没有足够的证据来证明地球上化学的基本组成部分--五元环和六元环。尽管在过去50年中作出了长期和持续的努力。相比之下，一种特殊的结构基序，高度不饱和的碳在链状排列中，在太空中却很常见。最近天文学在黑暗分子云TMC-1中探测到了苯甲腈（最简单的芳香腈），不久之后又在星前和可能的原恒星源中探测到了苯甲腈，这表明芳香化学很可能在星星形成的早期阶段广泛存在。随后在TMC-1中发现了氰基环戊二烯，甚至氰基萘，这进一步证明了相当复杂的有机分子很容易在具有高视觉消光但低温和低压非常低的区域合成。这篇评论的重点是实验室的努力，现在正在进行了解丰富的过渡区之间的线性和平面碳结构，使用微波光谱。我们目前的检测方法的主要特点，优点和缺点，在空间和实验室中发现的分子类型的讨论，以及正在开发的方法来识别复杂混合物中的全新物种。着重于烃的氰化和苯的形成从无环前体的研究突出，是同位素研究可能发挥的作用，在阐明环形成的化学途径。
Astrochemistry lies at the nexus of astronomy, chemistry, and molecular physics. On the basis of precise laboratory data, a rich collection of more than 200 familiar and exotic molecules have been identified in the interstellar medium, the vast majority by their unique rotational fingerprint. Despite this large body of work, there is scant evidence in the radio band for the basic building blocks of chemistry on earth-five and six-membered rings. despite long-standing and sustained efforts during the past 50 years. In contrast, a peculiar structural motif, highly unsaturated carbon in a chainlike arrangement, is instead quite common in space. The recent astronomical detection of cyanobenzene, the simplest aromatic nitrile, in the dark molecular cloud TMC-1, and soon afterward in additional prestellar and possibly protostellar sources, establishes that aromatic chemistry is likely widespread in the earliest stages of star formation. The subsequent discovery of cyanocyclopentadienes and even cyanonaphthalenes in TMC-1 provides further evidence that organic molecules of considerable complexity are readily synthesized in regions with high visual extinction but where the low temperature and pressure are remarkably low. This review focuses on laboratory efforts now underway to understand the rich transition region between linear and planar carbon structures using microwave spectroscopy. We present key features, advantages, and disadvantages of current detection methods, a discussion of the types of molecules found in space and in the laboratory, and approaches under development to identify entirely new species in complex mixtures. Studies focusing on the cyanation of hydrocarbons and the formation of benzene from acyclic precursors are highlighted, as is the role that isotopic studies might play in elucidating the chemical pathways to ring formation.