Question
Fri May 27, 2011 By: Priya Das

plz answer

Expert Reply
Fri May 27, 2011
Aldol condensation is a self condensation reaction  of aldehydes and ketones having ? - hydrogen (hudrogen attached to the carbon atom adjacent to the carbonyl group) in the presence of dilute alkali to form ? - hydroxy aldehyde or ? - hydroxy ketone . The products are commonly called aldols derived from the coombination of words aldehyde and alcohol because products have both these functional group.
In the presence of NaOH
2 CH3CHO ? CH3CHOHCH2CHO
Acetaldehyde     Aldol
 
Mechanism:
 
1.OH- abstracts h+ fromone acetaldehyde molecule to form resonance stabilised enolate ion
 
HO- + H-CH2CHO ? -CH2CHO
 
2. Enolate ion being a nucleophile attacks carbonyl carbon of other acetaldehyde molecule
 
 
CH3CHO +  -CH2CHO ? CH3CHO-CH2CHO
acetaldehyde  Enolate ion    Anion
 
3. The anion formed abstacts proton from water to form aldol.
 
CH3CHO-CH2CHO + H2O ? CH3CHOHCH2CHO
Anion                                    Aldol
 
 
 
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