Structure-Reactivity Relationships in Carbanion Chemistry

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The focus of this research is the investigation of how N,N,N',N'-tetramethylethylenediamine (TMEDA) and related diamines modify, or fail to modify, organolithium aggregate structures and reactivity. Structural studies with NMR will use TMEDA and related diamines with n-butyllithium, phenyllithium, lithium acetylides and related organolithium derivatives. Comparisons and competitions of diamines with tetrahydrofuran and related ethereal ligands will ascertain the circumstances under which the ethers bind competitively or cooperatively to organolithiums. Quantitative ligand binding studies will establish thermochemical foundations for subsequent rate studies. Rate data for representative reactions of diamine-solvated organolithium derivatives, in the context of well-established solution structure assignments, will afford insights into the solvation and aggregation events proceeding to the rate limiting transition structures. Dissection of solvation effects into ground state and transition state contributions will be central to an understanding of TMEDA's role in organolithium chemistry. With this renewal award, the Organic and Macromolecular Chemistry Program is supporting the research of Dr. David B. Collum of the Department of Chemistry at Cornell University. Professor Collum will focus his work on challenging the existing notions on how N,N,N',N'-tetramethylethylenediamine (TMEDA) and related diamines influence organolithium structures and reactivities. The research has substantial implications for organic synthesis due to the wide spread use of organolithium reagents.