CHED 424 |
| The hydrophobic effect is the tendency for nonpolar surfaces to aggregate in water and can be used to control the geometry of reacting species in order to obtain selectivities unique to the aqueous medium. Amine boranes bearing hydrophobic groups were synthesized and used to study the selectivity of ketone reductions. In methanol, both lithium borohydride and ammonia borane showed a preference for the reduction of acetyl groups over competing phenyl and naphthyl ketones; however, when amine boranes bearing hydrophobic groups were used, a reversal of this selectivity was observed. Using pentafluorobenzylamine borane, a seven-fold rate acceleration was observed for the reduction of naphthyl ketone as compared to the same reaction with lithium borohydride. Solvent and salt effects were consistent with the involvement of hydrophobic packing in the transition state of the reaction between hydrophobic amine boranes and aryl ketones. |
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Undergraduate Research Poster Session: Organic Chemistry
11:15 AM-1:15 PM, Monday, 14 March 2005 Convention Center -- Hall D, Poster
Division of Chemical Education |