Unsaturated Hydrocarbon Cation Radical Chemistry

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This grant in Organic and Macromolecular Chemistry provides support for the research of Professor Stephen Nelsen, University of Wisconsin, whose work focuses on the chemistry of organic radical cations. Such species are thought to be important intermediates in a number of oxidation processes. A full understanding of oxidation processes has important practical implications in controlling a variety of oxidations, particularly ones that are destructive to organic molecules. Changes in nuclear and electronic structure upon electron removal from unsaturated hydrocarbon derivatives will be probed by optical and ESR spectroscopy, PE spectroscopy and cyclic voltammetry. Energy differences in the gas phase and in solution between the neutral and ionic state will be determined. Semiempirical calculations will also be carried out. A series of sesquibicyclic alkenes, which will change the amount of pyramidalization which occurs upon electron loss, will be prepared. Comparison of compounds with C=C+. as the formal charge-bearing center with other compounds having the same alkyl groups but NN+. bearing the charge will reveal differences in sigma, pi interactions. Chemistry initiated by irradiation into the sigma, pi transition of these compounds will also be surveyed. Studies of CO bond formation upon chain reaction of dioxygen with these compounds (initiated by their cation radicals) will continue. Unusual selectivities result from the peroxyl-carbocation and peroxide cation radical intermediates, and four, five, and six-membered ring peroxides (dioxetanes, dioxolanes, and endoperoxides), many of which are not available by other methods, have been shown to be formed. Extensions of this Cation Radical Chain Catalyzed (CRCC) chemistry to additions of carbon monoxide, isonitriles, nitrous oxide, and acetylenes will be explored.