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Chapter 18: Enols and Enolates



Overview of Enolate Reactions | Alpha-Halogenation fo Aldehydes and Ketones | Haloform reaction | Alkylation of Enolates | The Aldol Condensations of Aldehydes | Conjugated Systems...Implications | The Michael Addition Reaction | The Robinson Annulation Reaction |


Alpha-Halogenation of Aldehydes and Ketones

Chapter 18: Enols and Enolates

 

alpha halogenation of aldehydes and ketones

Reaction type : Nucleophilic substitution

Summary

Related Reactions
MECHANISM OF a-HALOGENATION OF ALDEHYDES AND KETONES 
Step 1:
First, tautomerize the carbonyl to its enol tautomer (mechanism not shown here : review)
mechanism of halogenation of aldehydes and ketones
Step 2:
Here the electrons from the oxygen are used as they enhance the nucleophilicity of the alkene, as a result we end up with an oxonium ion and a bromide ion.
Step 3:
An acid / base reaction. Here the bromide ion is used to deprotonate the oxonium ion.

 

Basic a-Halogenation of Aldehydes and Ketones

Reaction type : Nucleophilic substitution

Summary

Related Reactions
MECHANISM OF a-HALOGENATION OF ALDEHYDES AND KETONES UNDER BASIC CONDITIONS
Step 1:
First, an acid-base reaction. Hydroxide functions a s a base and removes the acidic a-hydrogen giving the enolate.
mechanism of basic halogenation of aldehydes and ketones
Step 2:
The nucleophilic enolate reacts with the halide giving the halogenated ketone and a bromide ion.
 

 
 
 


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