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

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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.