Gas-Phase Studies of Charged Aromatic Radicals and Biradicals

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With this renewal award the Organic and Macromolecular Chemistry Program supports the work of Dr. Hilkka I. Kenttamaa of the Department of Chemistry at Purdue University in West Lafayette, Indiana. The purpose of this work is to generate aromatic biradicals (1,n-arynes) in the gas phase, and study their product branching ratios and rate constants in reactions with atom donors, electophiles, nucleophiles, and stable radicals. Each biradical carries a chemically inert charged substituent that allows it and its reaction products to be studied by Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR). Structural features of the biradicals will be varied, including the distance and orientation of the two radical sigma-orbital lobes, the type of charged group, and the presence of additional substituents. Reactivity-controlling parameters to be investigated include the biradicals' singlet-triplet gaps and the polarity of their transition states. Experimental studies will be complemented by molecular orbital calculations.The proposed research is at the frontiers of mass spectrometry in studies of short-lived reaction intermediates. The fundamental information to be obtained is likely to be of great interest to organic and organometallic chemists who use radicals and biradicals in synthesis. The PI has a large group of undergraduate and graduate students, about half of whom are female or from underrepresented groups. For them the research is expected to provide a valuable educational experience.