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·麦克马洪教授得到了有机化学和高分子化学计划的支持，他的研究旨在阐明星际空间中有机分子的身份、结构、性质和反应性。实验和计算研究相结合的研究重点是已知或可能存在于星际介质中的有机物种。这些有机物种将在实验室中产生，并通过红外、紫外/可见光、电子自旋共振和微波光谱对其分子结构进行研究。为了解决星际空间中环状芳香族物种的存在问题，以及已被证明存在的非环分子形成环状芳香族物种的机制，我们将研究开链有机分子闭环的基本化学机制。更多的研究将试图通过实验室旋转光谱和随后的射电天文搜索相结合的方式来探测星际介质中的芳香族物种及其前体。所谓的“星际扩散带”的起源被描述为现代天文学和分子光谱学的基本问题之一。目前，还不清楚星际空间中是否存在表现出不寻常的稳定性的环状物种，即芳香性，如果是这样的话，这些物种是如何由已知存在的非环分子形成的。在有机化学和高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旨在解决这些问题的实验和计算研究相结合的研究。麦克马洪教授通过制备芳香族化合物的非环前体并研究它们的结构和反应性，探索了星际空间中可能发生的基本反应化学反应。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.