ENOLS AND ENOLATES47118.2As shown in the general equation and the examples, halogen substitution is specifc For the a-carbonatom. The ketone 2-butanone has two nonequivalent acarbons, and so substitution is possible atboth positions. Both 1-chloro-2-butanone and 3-chloro-2-butanone are Formed in the reaction.18.3The carbon–carbon double bond oF the enol always involves the original carbonyl carbon and thea-carbon atom. 2-Butanone can Form two diFFerent enols, each oF which yields a diFFerent a-chloroketone.18.4Chlorine attacks the carbon–carbon double bond oF each enol.18.5(b)Acetophenone can enolize only in the direction oF the methyl group.(c)Enolization oF 2-methylcyclohexanone can take place in two diFFerent directions.
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