Ch 17 orgo notes - Ch 17:Enols and Enolate Anions as...

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Ch 17:Enols and Enolate Anions as Nucleophiles. Alkylation and Condensation Reactions Enols and enolate anions are nucleophiles and react with electrophiles The electrophile may be a halogen, an alkyl halide, or a carbonyl compound Enolate ions also add to double bonds that are conjugated w/ a carbonyl group When enolate anions react as nucs w/ electrophilic carbon atoms, C-C bonds are formed o Important for syntheses!! 17.1 Rxns of Enols and Enolates w/ halogens as electrophiles o ex, enol of acetone reacts w/ bromine to give 1-bromo-2-propanone o bromine is the electrophile that reacts w/ nucleophilic enol o the rate of halogenation depends only on the concentration of ketone o formation of the enol from the ketone is the rds 17.2 Reactions of Enolate Anions w/ alkyl halides as electrophiles o enolate anions react w/ alkyl halides in nucleophilic substituion rxns known as alkylation rxns o 2 resonance contributors of the enolate anion exist: the enolate ion has e- density and negative charge at two sites it is basic and nucleophilic at the alpha carbon and at the oxygen atom of the carbonyl group can be protonated or can react w/ electrophiles at either of these sites an anion that has the capacity to react at either of 2 positions is called an ambident anion where it reacts depends on reaction conditions generally, carbon electrophiles favor alkylation at the carbon atom o lithium diisopropylamide is a strong base but a poor nuc so fewer side products; deprotonates the ketone on the less substituted side (kinetic) o alkylation of esters enolate anions of esters can also be prepared using lithium
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This note was uploaded on 03/07/2010 for the course CHEM 215 taught by Professor Koreeda during the Spring '07 term at University of Michigan.

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Ch 17 orgo notes - Ch 17:Enols and Enolate Anions as...

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