Mechanisms of Bond-Making and Bond-Breaking; Role of RadicalIons (Chemistry)

有机化学和高分子化学项目的这项拨款支持弗雷德里克·格林教授的研究，其核心是阐明反应机理。反应机理是构成化学反应的成键和断键的详细序列；了解这些过程及其控制因素是控制化学反应活性的关键因素。格林博士的研究将集中在通过催化和非催化方法形成和断裂键的机制上。这项工作将探索一种相对较新的方式，通过“电子催化”来启动有机反应，即：在反应物中添加或移除一个电子，以形成高活性的自由基离子。虽然人们对被称为自由基(未配对电子)和离子(带电)的活性中间体的基团了解很多，但目前对自由基离子的化学了解要少得多，因为自由基离子是也带电荷的奇电子物种。格林小组的一个主要目标是获得有关自由基离子化学性质的新信息。计划进行一项探索性研究，考察自由基离子在选择性加成、环加成、逆环加成和重排反应中的作用。将对各种电子给体和受体进行评估，注意电化学信息和对新给体的一些考虑。四元环偶氮化合物(二氮杂环)的逆环加成反应构成了断键过程机理的一个重要测试案例。最近的结果为合成所需物质提供了有希望的路线。实验还计划探索电子受体引发的二氮杂环后加成反应的机理。

This grant in the Organic and Macromolecular Chemistry Program supports reserach by Prof. Frederick Greene, which is centered around the elucidation of reaction mechanisms. Reaction mechanisms are the detailed sequences of bond-making and bond- breaking which constitute chemical change; understanding these processes and their controlling factors is a critical element in controlling chemical reactivity. Dr. Greene's research will focus on the mechanisms of bond formation and rupture by both catalytic and non-catalytic means. This work will pursue a relatively new way of initiating organic reactions by "electron catalysis," that is: the addition or removal of an electron from a reactant to form a highly reactive radical ion. Although much is known about the groups of reactive intermediates known as radicals (unpaired electrons) and ions (electrically charged), much less is currently known about the chemistry of radical ions, which are odd-electron species also carrying charge. A major objective of the Greene group is to obtain new information on the chemical properties of radical ions. An exploratory study is planned to examine the role of radical ions in selected addition, cycloaddition, retrocyclo- addition, and rearrangement reactions. Various electron donors and acceptors will be evaluated, with attention to electrochemical information and to some consideration of new donors. Retrocycloaddition reactions of four-membered ring cyclic azo compounds (diazetines) constitute an important test case for mechanisms of bond-breaking processes. Recent results have provided promising routes for syntheses of substances needed. Experiments are also planned to probe the mechanism of retrocycloaddition of diazetines initiated by electron acceptors.