Lithium Carbenoids and Related Species: Structure and Reactions

化学结构、动力学和机制计划支持田纳西州纳什维尔菲斯克大学的劳伦斯·M·普拉特教授和夏威夷大学的马库斯·A·蒂乌斯教授继续努力，更好地了解锂类卡宾的结构和反应机理。该项目将使用计算量子化学和核磁共振光谱相结合的方法来确定锂卡宾在溶液中的结构，以及它们与其他锂化合物形成混合聚集体的倾向。混合聚集体在有机锂化学中是众所周知的，它们有时对反应活性和选择性有很大的影响。到目前为止，所研究的反应机理往往非常复杂，如果不使用计算化学，将很难阐明。在最初的赠款期间完成的初步工作表明，哪些计算方法最适合本研究中的问题。从计算的反应机理中得到的反应产物的预测将在TIUS合成小组的实验室中得到验证。通常，两个或多个反应机理同时运行，改变反应条件可以增强或抑制一个机理。这有时会导致反应选择性的提高，产品的纯度提高，有毒废物的产生减少。在国家科学基金会化学部化学结构、动力学和机理计划的支持下，田纳西州纳什维尔菲斯克大学的劳伦斯·M·普拉特教授和夏威夷大学的马库斯·A·蒂乌斯教授将有助于进一步了解锂类卡宾反应，从而在合成有机反应中得到更广泛的应用。有机锂试剂在现代合成中普遍存在，但对影响其结构和反应活性的因素知之甚少。更广泛的影响是在学生教育和培训方面，对少数民族学生的影响最大。菲斯克大学是一所历史悠久的黑人学院/大学(HBCU)，大约98%的非裔美国人和大约70%的女性学生。夏威夷大学是一个合作机构，也致力于将少数族裔纳入科学领域。路易斯安那理工大学也是一所合作机构，拥有大量的非裔美国学生，并与另一所HBCU格拉姆布林州立大学(Gramling State University)联合任命了一些教职人员。这项研究的主要影响将是重振菲斯克大学的研究生(MS)项目，该项目近年来受到经济状况的影响。这个项目的一个目标是帮助这些学生进入他们选择的项目，可能是在与普拉特教授在这个项目和其他项目上合作的几所研究型大学中的一所。

The Chemical Structure, Dynamics and Mechanisms Program supports Professors Lawrence M. Pratt, at Fisk University in Nashville TN, and Marcus A. Tius at the University of Hawaii who will continue their efforts to better understand the structures and reaction mechanisms of lithium carbenoids. The project will use a combination of computational quantum chemistry and NMR spectroscopy to determine the structure of lithium carbenoids in solution, and their tendency to form mixed aggregates with other lithium compounds. Mixed aggregates are well known in organolithium chemistry, and they sometimes have dramatic effects on reactivity and selectivity. The reaction mechanisms studied to date have often been quite complex, and would be very difficult to elucidate without the use of computational chemistry. Preliminary work completed during the initial grant period has shown which computational methods are most appropriate for the problems in this study. The predictions of the reaction products, obtained from the calculated mechanisms, will be tested in the laboratory of the Tius synthetic group. Frequently, two or more reaction mechanisms are operating concurrently, and changing the reaction conditions may enhance or suppress one mechanism. This sometimes results in improved reaction selectivity, purer products, and reductions in the production of toxic wastes. It may also show that the reagents being investigated are not ideal for a particular reaction, and may spur the search for alternate synthetic methods.With the support of the Chemical Structure, Dynamics and Mechanisms Program in the Chemistry Division at the National Science Foundation, Professors Lawrence M. Pratt, at Fisk University in Nashville TN, and Marcus A. Tius at the University of Hawaii will contribute to further understanding of lithium carbenoid reactions that can lead to a wider application in synthetic organic reactions. Organolithium reagents are ubiquitous in modern synthesis but little is known about the factors affecting their structure and reactivity. Broader impacts are in student education and training, with the largest impact on minority students. Fisk University is a Historically Black College/University (HBCU), with about 98% African-American and about 70% female students. The University of Hawaii is a collaborating institution, and is also committed to the inclusion of minorities in science. Louisiana Tech University is also a collaborating institution, with a large African-American student population and some joint faculty appointments with Grambling State University, another HBCU. A major impact of this research will be to revitalize the graduate (MS) program at Fisk, which had been hurt by economic conditions in recent years. A goal of this project is to help those students bridge into a program of their choice, possibly at one of the several research universities collaborating with Professor Pratt on this and other projects.