Rearrangements of Carbenes and Diazirine Excited States

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Dr. Matthew S. Platz of the Department of Chemistry at Ohio State University is supported by a grant from the Organic Dynamics Program to continue his studies of the rearrangements of carbenes and excited states of diazirines. He will study alkyl, dialkyl, cycloalkyl, and acyl carbenes generated by laser flash photolysis of nitrogenous and non-nitrogenous precursors, examining the influence of carbene structure and isotopic composition, temperature, and solvent polarity on the rate of carbene rearrangement. Calculational studies will address the possible roles of quantum mechanical tunneling and dynamical effects in these rearrangements. Rearrangement and cleavage mechanisms of diazirines will be probed by low-temperature high resolution fluorescence spectroscopy. New types of carbene precursors, more efficient than those currently used, will be used to generate carbenes at low temperature, allowing their study by UV-visible and infrared spectroscopy and experimentally addressing the issue of ground state electronic structure for simple dialkyl carbenes. In contrast to typical stable organic compounds, which are based on carbon atoms connected to four other atoms, carbenes, which contain carbon bonded to only two other atoms, are high-energy compounds. None-the-less, carbenes appear to be formed in a large number of chemical reactions, and development of an understanding of their properties and chemistry remains an important research goal. Professor Platz will study the influence of several critical variables on the reaction chemistry of carbenes and will couple these studies with calculational work in order to assess the influence of electronic structure and quantum mechanical effects on these reactions. He will prepare organic compounds which serve as precursors to carbenes, allowing the formation of ordinarily reactive carbenes under conditions which permit their experimental study, and will analyze the chemistry of other carbene precursors, widely used throughout the world research community, which appear to display more complex chemistry than generally appreciated.