Ground and Excited State Chemistry of Diazirines and Carbenes

9314894 Platz将研究通过光化学方法生成卡宾以及这些过渡中间体的反应。实验将提供有关卡宾的几何构型、单重态/三重态能级、生成热以及分子内和分子间反应速率的基本信息。重点将放在了解烷基卡宾的重排，在那里观察到低的活化热和大的负活化熵。特别是，隧道效应的可能性将被用来解释不寻常的激活参数。将详细研究激发态二氮杂环的化学，因为这些卡宾的前体可能模仿卡宾的一些化学。沿着反应面的几个点将被表征为激发态二氮杂环的反应。%有机动力学项目的这笔赠款支持俄亥俄州立大学马修·S·普拉茨教授的继续工作。卡宾是一种高能化合物，它只与碳中的其他元素形成两个键，而稳定的碳化合物中包含四个与其他元素的键。在大量的反应中，会产生卡宾中间体。这些转瞬即逝的中间体的寿命将取决于卡宾的结构、溶剂的极性和温度。这些研究将导致对这些重要中间体及其在合成中的应用有一个基本的了解。***

9314894 Platz The generation of carbenes by photochemical methods and reactions of these transient intermediates will be studied. Experiments will be carried out to provide fundamental information about the geometry, singlet/triplet energy levels, heats of formation, and rates of intra-and intermolecular reactions of carbenes. An emphasis will placed on understanding the rearrangement of alkyl carbenes, where low activation enthalpies and large negative entropies of activation have been observed. In particular, the possibility of tunneling as an explanation for the unusual activation parameters will be pursued. The chemistry of excited state diazirines will be studied in detail, since these precursors to carbenes may mimic some of the chemistry of carbenes. Several points along the reaction surface will be characterized for the reaction of excited state diazirines. %%% This grant from the Organic Dynamics Program supports the continuing work of Professor Matthew S. Platz at Ohio State University. Carbenes are high energy compounds which contain only two bonds to other elements from carbon, while stable compounds of carbon contain four bonds to other elements. In a large number of reactions, carbene intermediates are generated. The lifetimes of these fleeting intermediates will be determined as a function of structure of the carbene, solvent polarity, and temperature. These studies will lead to a basic understanding of these important intermediates and to their use in synthesis. ***