Structure and Mechanisms in Annulenes and Polycyclic Aromatic Hydrocarbons

碳氢化合物是一类基本的有机化合物。尽管事实上它们只包含两种元素，碳和氢，但令人眼花缭乱的各种可能的（和已知的）碳氢化合物结构为化学家提供了一种研究分子关键特性的方法，从化学键的本质到复杂反应的详细机制。目前的计算研究主要集中在两个亚类碳氢化合物：环烯和多环芳烃。这些化合物中的高碳氢比使它们对了解富碳材料的性质很有用，包括富勒烯和碳纳米管。该项目将雇用本科生，并为他们提供计算化学基本知识的培训。该小组先前对环烯（苯的类似物，带有数字表示环上的碳数）的研究表明，[12]环烯，[14]环烯和[16]环烯的顺反异构化是通过具有Möbius条拓扑结构的过渡态的双键转移发生的。一个新的项目将是确定异构化是否可以发生在其他拓扑结构中，如平面和双扭（图8）形式。此外，该小组将尝试通过计算设计一个稳定的Möbius芳香环烯。最后，受最近关于脱氢[12]环烯（[12]环烯有一个三键）的实验结果的启发，该小组打算产生关于该体系的许多可能的异构体的结构，相对能量和预测的NMR谱的详细信息，以及可能的重排和构象运动的能量垒。该项目还将为本科生提供宝贵的培训。因为这项工作借鉴了有机化学和物理化学的基本概念，所以对许多学生来说特别有吸引力，也很容易理解，因此为他们提供了一个绝佳的研究机会。考虑到旧金山大学的学生群体高度多样化，吸纳科学领域代表性不足群体的成员，尤其是女性，具有特别的潜力。学生将获得广泛的计算技术的经验，包括潜在的表面扫描，过渡状态的位置和属性的计算。简而言之，该项目将为未来应用量子力学解决化学问题的专家提供培训。

Hydrocarbons constitute a fundamental class of organic compounds. Despite the fact that they contain only two elements,carbon and hydrogen, the dazzling variety of possible (and known) hydrocarbon structures provides chemists with a means to study key properties of molecules, from the nature of chemical bonding to detailed mechanisms of complex reactions. The present computational study focuses on two subclasses of hydrocarbons: annulenes and polycyclic aromatic hydrocarbons. The high carbon-to-hydrogen ratio in these compounds makes them useful for understanding properties of carbon-rich materials, including fullerenes and carbon nanotubes. The project will employ undergraduates and provide them with training in essentials of computational chemistry. The group's previous studies on annulenes (analogues of benzene with a number indicating the number of carbons in the ring) revealed that cis-trans isomerization in [12]annulene, [14]annulene, and [16]annulene occurs by double-bond shifting via a transition state having the topology of a Möbius strip. One new project will be to determine whether isomerization can occur in other topologies, such as planar and two-twist (figure-eight) forms. In addition, the group will attempt to computationally design a stable Möbius aromatic annulene. Finally, inspired by recent experimental results on dehydro[12]annulene ([12]annulene with a triple bond), the group intends to generate detailed information on the structures, relative energies, and predicted NMR spectra of the numerous possible isomers of this system, as well as the energy barriers for possible rearrangements and conformational motions. This project will also provide valuable training for undergraduates. Because the work draws on fundamental concepts taught in organic and physical chemistry, it is particularly appealing and accessible to many students, and thus represents an excellent opportunity to engage them in research. Given the highly diverse student population at the University of San Francisco, there is particular potential for involving members of underrepresented groups in science, especially women. Students will gain experience in a wide range of computational techniques, including potential surface scans, location of transition states, and calculation of properties. In short, the project will provide training for future experts in the application of quantum mechanics to the solution of chemical problems.