ORGN 563 |
| Antonio Facchetti, Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 and Andrew Streitwieser, Chemistry, University of California, Berkeley, CA 94720. |
| Equilibrium mono- (-M) and dimetal (-M2) (M=Li, Cs) ion pair acidities at 25 °C have been investigated in THF for the following b-dicarbonyl compounds: 1-(4-Biphenylyl)butane-1,3-dione (1), 1,4-diphenylbutane-1,3-dione (2), and 6,7,8,9-tetrahydro-5H-benzocyclohepten-5,7-dione (3). While second acidity data for this class of compounds are essentially unknown in the literature, the trend of the first acidities was compared with those previously reported for similar systems in DMSO. Studies of their acidities over a wide range of concentrations indicate that mono lithium enolates 1-Li, 2-Li, and 3-Li strongly aggregate. In contrast, the corresponding dilithium enolates 1-Li2, 2-Li2, and 3-Li2 are essentially monomeric. Large amounts of dimer were also detected for the cesium enolates 1-Cs, 2-Cs, and 2-Cs2. Finally, we performed a combined 1H and 13C NMR study in both THF-d8 and DMSO-d6 to gain useful insights into the homogeneous keto-enol equilibria of 1-3 and the structures of the corresponding mono- and dienolate species in solution. |
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Heterocycles, Aromatics, Metal-Mediated Reactions, Physical Organic, Materials
9:00 AM-11:00 AM, Wednesday, March 26, 2003 Convention Center -- Hall I-1, Poster
Division of Organic Chemistry |