Mechanistic Studies of Organic Reactivity

Professor Jeehiun Katherine Lee of the Department of Chemistry at Rutgers University will utilize funding provided by the Chemical Mechanism, Function, and Properties Program of the Chemistry Division to explore organic reactivity and mechanism. One focus will be on reactions catalyzed by N-heterocyclic carbenes (NHCs). NHCs are novel organic substances that increase the speed of various important chemical reactions. Their mechanisms, however, are still poorly understood. The work will utilize both computational and experimental methods, primarily in the gas phase, to reveal intrinsic reactivity. The project has the potential to improve understanding of these catalytic compounds, which will in turn improve their efficiency and utility. This would potentially positively impact synthetic methods that utilize NHCs, which will in turn impact many areas of chemistry, including pharmaceuticals and other useful chemicals. Another focus will be on the properties of reactants, the "players" in a reaction. The properties of "nucleophilicity" and "electrophilicity" will be examined in the absence of solvent, to better understand inherent reactivity of organic species. These fundamental mechanistic studies will also provide education and training for scientists at all levels. N-heterocyclic carbenes (NHCs) are important players in organic chemistry, both as ligands and as catalysts. As organocatalysts, NHCs are best known for their ability to effect Umpolung: the reversal of polarity/reactivity of the carbonyl carbon of a given substrate. These reactions are of great synthetic utility, but mechanistic questions abound. Because examination of these reactions can be complicated by solvent, this chemistry will be examined in the gas phase, using both experimental (mass spectrometric) and computational (quantum mechanical) methods. The mechanisms by which the polarity reversal is incurred will be examined, with the overall goal of developing improved catalysts. Also, gas phase nucleophilicity and electrophilicity of silane and carbon hydrides will be probed, to move toward the development of a gas phase nucleophilicity-electrophilicity scale. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.