Lithium diisopropylamide (LDA)-mediated alpha- and beta-eliminations of epoxides an described. A comparison between LDA/n-BuOMe mixtures and LDA/MeOCH2CH2NMe2 (LDA/3) mixtures reveals that the LDA dimer solvated by the "hemi-labile" amino ether 3 imparts dramatic rate accelerations, alters relative efficacies of monomer- and dimer-based metalations, and influences the partitioning between alpha- and beta-metalation. The alpha-elimination of exo-norbornene oxide by LDA/n-BuOMe and LDA/3 proceeds exclusively via a dimer-based pathway with a transition structure, [(R2NLi)(2)(epoxide)(ligand)](double dagger). The beta-elimination of tetramethylethylene oxide by LDA/n-BuOMe and LDA/3 proceeds exclusively via a monomer-based pathway with a transition structure, [(R2NLi)(epoxide)(ligand)](double dagger). cis-Cyclooctene epoxide reacts with LDA/3 to give two products: (1) a bicyclooctanol derived from an alpha-metalation and a dimer-based transition structure, [(R2NLi)(2)(epoxide)(ligand)](double dagger), and (2) 2-cycloocten-1-ol derived from both a monomer-based transition structure, [(R2NLi)(epoxide)(ligand)](double dagger), and a dimer-based transition structure, [(R2NLi)(2)(epoxide)(ligand)](double dagger). Possible geometries of the transition structures are discussed. Hemi-labile ligands that chelate lithium only at the rate-limiting transition structures maximize both the reaction rates and the mechanistic transparency.