Ground and Excited State Chemistry of Diazirines and Carbenes

本文将研究用光化学方法生成碳烯，以及这些过渡中间体的反应。实验将提供有关碳烯的几何结构、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。重点将放在理解烷基羰基的重排，其中低活化焓和大的负活化熵已被观察到。特别是，隧道效应作为异常激活参数的解释的可能性将被追求。我们将详细研究激发态氮嘧啶的化学性质，因为这些碳烯的前体可能模仿碳烯的某些化学性质。反应表面上的几个点将被表征为激发态氮嘧啶的反应。这项来自有机动力学项目的资助支持俄亥俄州立大学Matthew S. Platz教授的持续工作。碳烯是一种高能化合物，它与碳的其他元素只有两个键，而稳定的碳化合物与其他元素有四个键。在大量的反应中，会产生碳中间体。这些转瞬即逝的中间体的寿命将被确定为碳的结构、溶剂极性和温度的函数。这些研究将使我们对这些重要的中间体有一个基本的了解，并使我们对它们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. ***