Mechanistic Organic Chemistry of Relevance to the Interstellar Medium

威斯康星大学麦迪逊分校化学系的罗伯特·j·麦克马洪（Robert J. McMahon）教授得到了有机和大分子化学项目的资助，他的研究方向是阐明星际空间中有机分子的身份、结构、性质和反应性。实验和计算研究的结合集中在已知或可能存在于星际介质中的有机物种上。这些有机物质将在实验室中生成，并通过红外、紫外/可见光、电子自旋共振和微波光谱研究它们的分子结构。为了解决环芳香族物质在星际空间中存在的问题，以及它们由已证明存在的无环分子形成的机制，将研究开链有机分子进行环闭合的基本化学机制。进一步的研究将尝试通过实验室旋转光谱学和随后的射电天文搜索相结合来探测星际介质中的芳香物种及其前体。所谓的“漫射星际带”的起源已被描述为现代天文学和分子光谱学的基本问题之一。目前，我们还不能肯定地知道，在星际空间中是否存在具有不寻常稳定性的环状物质，即芳香性，如果存在，这些环状物质是如何从已知存在的非环状分子中形成的。在有机和大分子化学项目的支持下，威斯康星大学麦迪逊分校化学系的罗伯特·j·麦克马洪教授正在进行一项实验和计算相结合的研究，旨在解决这些问题。通过制备芳香物质的无环前体并研究它们的结构和反应性，麦克马洪教授探索了可能在星际空间发生的基本反应化学。通过用各种光谱技术探测这些物种，他既阐明了它们的结构，又提供了可能在星际介质中寻找的光谱“特征”，为这些物种的存在（或不存在）提供了证据。

Professor Robert J. McMahon, of the Department of Chemistry at the University of Wisconsin - Madison, is supported by the Organic and Macromolecular Chemistry Program for his studies directed toward the elucidation of the identity, structure, properties, and reactivity of organic molecules that occur in interstellar space. A combination of experimental and computational investigations are focused on organic species that are either known to or are likely to exist in the interstellar medium. These organic species will be generated in the laboratory, and their molecular structure investigated by infrared, ultraviolet/visible, electron spin resonance, and microwave spectrometry. In order to address the question of the existence of cyclic, aromatic species in interstellar space, as well as the mechanisms for their formation from acyclic molecules whose existence has been demonstrated, the fundamental chemical mechanisms by which open-chain organic molecules undergo ring closure will be investigated. Additional studies will attempt to detect aromatic species and their precursors in the interstellar medium through a combination of laboratory rotational spectroscopy and subsequent radio-astronomical searches.The origin of the so-called "diffuse interstellar bands" has been described as one of the fundamental problems in modern astronomy and molecular spectroscopy. At the present time, it is not known with certainty whether cyclic species displaying the unusual stabilization known as aromaticity exist in interstellar space and, if so, how these species can be formed from the acyclic molecules that are known to exist there. With the support of the Organic and Macromolecular Chemistry Program, Professor Robert J. McMahon, of the Department of Chemistry at the University of Wisconsin - Madison, is carrying out a combination of experimental and calculational studies designed to address these questions. By preparing acyclic precursors to aromatic species and examining their structure and reactivity, Professor McMahon explores the fundamental reaction chemistry which could occur in interstellar space. By probing these species with a variety of spectroscopic techniques, he both elucidates their structures and provides spectroscopic "signatures" which may be sought in the interstellar medium, providing evidence for the existence (or absence) of these species.