Lithium Carbenoids and Related Species: Structure and Reactions

化学结构、动力学和机制项目支持田纳西州纳什维尔菲斯克大学的Lawrence M. Pratt教授和夏威夷大学的Marcus A. Tius教授，他们将继续努力更好地了解类锂化合物的结构和反应机制。该项目将结合计算量子化学和核磁共振光谱来确定溶液中类锂化合物的结构，以及它们与其他锂化合物形成混合聚集体的趋势。混合聚集体在有机锂化学中是众所周知的，它们有时对反应性和选择性有显著的影响。迄今为止所研究的反应机制往往相当复杂，如果不使用计算化学就很难阐明。在最初拨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。从计算机制中得到的反应产物的预测将在Tius合成小组的实验室进行测试。通常，两种或两种以上的反应机制同时发生，改变反应条件可能会增强或抑制其中一种机制。这有时会提高反应选择性，提高产物纯度，减少有毒废物的产生。它也可能表明，正在研究的试剂不是理想的特定反应，并可能刺激寻找替代的合成方法。在美国国家科学基金会化学部化学结构、动力学和机制项目的支持下，田纳西州纳什维尔菲斯克大学的Lawrence M. Pratt教授和夏威夷大学的Marcus a . Tius教授将有助于进一步了解类碳锂反应，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无处不在，但对其结构和反应性的影响因素却知之甚少。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），约98%的非裔美国人和约70%的女学生。夏威夷大学是一个合作机构，也致力于将少数民族纳入科学领域。路易斯安那理工大学也是一所合作院校，拥有大量非裔美国学生，并与另一所HBCU——格兰布林州立大学（Grambling State University）联合聘用了一些教员。这项研究的一个主要影响将是振兴菲斯克大学的研究生项目，该项目近年来受到经济状况的影响。这个项目的目标是帮助这些学生进入他们选择的项目，可能是在几所研究型大学中的一所与普拉特教授合作进行这个和其他项目。

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.