Roles of Contact Ion-Pairs as Promoters or Catalysts in Organic Reactions

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The Chemical Synthesis Program of the NSF Chemistry Division supports the research, education, and outreach programs of Professor Gerald B. Hammond of the University of Louisville. This project is seeks new understanding of chemical reactions that rely on the formation of ions (charged particles). In an ionic reaction, ions can separate (dissociate) or they can form contact ion pairs (where they are just barely separated). Some solvents easily support the dissociation of ions (e.g., table salt in water). Other solvents do not allow ions to dissociate (e.g., table salt in oil). This research seeks to understand how the properties of the solvent affect the ion formation and separation and subsequently, how ion separation impacts the formation of reaction products. Experimental results are combined with various computational efforts to predict the structures of the ions/ion pairs in solution. Dr. Hammond inspires Hispanic students to enter chemistry and other science fields through his "Targeting Excellence: Hispanic Latino Student Initiative" which brings prominent Hispanic chemistry to the University to serve as role models. He is also establishing links with faculty in chemistry departments from Latin American Universities to attract high caliber research-active scientists and students in collaborative projects. Professor Hammond works with the California State University, Fresno to host undergraduate students for summer research and also collaborates with Professor Bo Xu, of Donghua University, China. With funding from the Chemical Catalysis Program of the Chemistry Division, Dr. Gerald B. Hammond, of the University of Louisville in Kentucky, is investigating ionic reactions. In an ionic reaction, ions can be dissociated or they can form contain ion pairs. This research examines how, in low dielectric constant and low solvation power solvents, contact ion pairs interact with reactants and catalysts in a chemical reaction. Ionic transformations cover a wide range of reaction types, from simple nucleophilic substitutions to complex cationic transition metal catalysis, but the understanding of counterion effects is mainly circumscribed to individual reactions. Toward this goal, his investigations generate affinity scales of counterions for various metal and non-metal groups and implement a new contact ion pair-assisted nucleophilic substitution process (SNip). This conceptually new nucleophilic substitution pathway enables reactivity in those instances where conventional SN2 or SN1 reactions fail. Computational studies of the SNip process are conducted. Also, under investigation is the design of ion pair promoters including chiral ion pair promoters and better electrophiles to facilitate the SNip process. Dr. Hammond is keenly engaged in outreach programs focused on underrepresented student recruitment into the technical fields through summer research internships.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.