Effect of Aromaticity and Anti-Aromaticity on Transition States and Intrinsic Barriers of Reactions

在有机化学和高分子化学项目的支持下，加州大学圣克鲁斯分校化学和生物化学系的克劳德·F·贝纳斯科尼教授将继续进行实验和计算研究，研究芳香性和反芳香性对一些基本化学反应的内在障碍的影响。对本征势垒的研究，即在没有热力学驱动力的情况下的势垒，可以对影响过渡态能量的因素进行批判性的评估，并有助于我们对化学反应速率的基本理解。在这些研究中将同时使用实验和计算方法。实验方法将涉及质子转移、高度亲电体系的亲核加成和氢化物离子转移的动力学和平衡测量。将选择允许调节产品或反应物中芳香性或反芳香性程度的反应，并通过实验确定固有势垒。计算方法将侧重于气相质子、氢化物离子、氢原子、卤离子以及涉及芳香族和反芳族物种的卤化物离子转移。将计算本征势垒，并将其与不涉及芳香族或反芳族物种的相应模型反应的各自势垒进行比较。这项研究的更广泛影响将是双重的。在科学层面，该项目解决了有关化学反应的基本问题，以及我们对结构如何影响化学反应的理解，这是物理有机化学的一个中心主题。在人力资源开发的层面上，拟议的工作为学生提供了广泛的教育经验，从合成和光谱表征到动力学、数据分析和计算化学。

With the support of the Organic and Macromolecular Chemistry Program, Professor Claude F. Bernasconi, of the Department of Chemistry and Biochemistry at the University of California, Santa Cruz, will continue experimental and computational studies of the effect of aromaticity and anti-aromaticity on the intrinsic barriers to a number of fundamental chemical reactions. Investigations of intrinsic barriers, that is the barriers in the absence of a thermodynamic driving force, allow critical evaluation of the factors affecting transition state energies and contribute to our basic understanding of the rates of chemical reactions. Both experimental and computational approaches will be used in these investigations. The experimental approach will involve kinetic and equilibrium measurements of proton transfers, nucleophilic additions to highly electrophilic systems, and hydride ion transfers. Reactions will be chosen which allow modulation of the degree of aromaticity or anti-aromaticity in products or reactants and intrinsic barriers will be determined experimentally. The computational approach will focus on gas phase proton, hydride ion, hydrogen atom, halonium ion, and halide ion transfers involving aromatic and anti-aromatic species. Intrinsic barriers will be calculated and compared to the respective barriers of corresponding model reactions that do not involve aromatic or anti-aromatic species. The broader impacts of this research will be two-fold. At the scientific level, the project addresses fundamental questions about chemical reactions and our understanding of how structure affects chemical reactivity, a central theme of physical organic chemistry. At the level of human resource development, the proposed work provides students with a broad educational experience, ranging from synthesis and spectroscopic characterization to kinetics, data analysis, and computational chemistry.