ALDOL CONDENSATION BY VANA JAGAN MOHAN RAO

1. BY
VANA JAGAN MOHAN RAO M.S.Pharm, MED.CHEM
NIPER-KOLKATA
Asst.Professor, MIPER-KURNOOL
e-mail: jaganvana6@gmail.com

2. Condensation between two molecules of an
Aldehyde or a Ketone to form a β-hydroxy aldehyde or
a β-hydroxy ketone is known as a ALDOL
CONDENSATION.
ALDOL CONDENSATION is possible only when the
carbonyl compound contains atleast one α-hydrogen
atom.

3. Enolizable aldehydes and enolizable ketones, in the presence of
an acid or base catalyst in aqueous medium at high temperature,
undergo a reaction, giving an α,β-unsaturated aldehyde or an α,β-
unsaturated ketone, respectively, as the product.
This reaction is known as aldol condensation. The base-catalyzed
aldol condensation, in which the catalyst is usually the hydroxide
ion, is more common.

4. REACTION:
MECHANISM:
Step 1: The hydroxide ion deprotonates the aldehyde reversibly.

5. Step 2: Enolate ion (1) adds to the unreacted aldehyde.
Step 3: Alkoxide ion (2) is protonated by water.

6. Step 4: Aldol (3) is an enolizable aldehyde. A small amount of it is converted to
the corresponding enolate ion (4) by the hydroxide ion.
Step 5: Enolate ion (4) loses a hydroxide ion.
Step 1,2,3 are an aldol reaction and Step 4,5 a 1,2-elimination via E1cB
mechanism.
Thus, aldol condensation is aldol reaction followed by 1,2-elimination.

7. ACID CATALYZED ALDOL REACTION MECHANISM

8. BASE CATALYZED ALDOL REACTION MECHANISM

9. A reversibleequilibrium
 OH is the base typically used in an aldol reaction.
 Aldol reactionscan be carried out with eitheraldehydes or
ketones.
With aldehydes, the equilibrium favorsproducts
 With ketones theequilibrium favors thestarting materials.
CONDITIONS FOR ALDOL CONDENSATION

10.  The aldol condensation is facilitated by-I groups on
thecarbonyl componentand retarted by +I groupsas
described in CHзCHO and CHзCOCHз
condensations.
 Thecondensation is readily reversibleand the position
of equilibrium is notalways favorable to the product.
 Eg:

11. LIMITATIONS:
Aldol products,as such, are not always isolated
from the reaction mixture.eg:acetaldol readily formsa
cyclic hemi-acetol.
EXTENSIONS:
Aldol condensation can occurbetween
 Two identical or differentaldehydes
 Two identical or differentketones
 An aldehyde and aketone

12.  The R groups may be H, alkyl, oraryl. When the R groups
in one molecule are different than those in the other, the
reaction is called a crossed-aldol reaction. The ability to
join differentaldehydes and ketones together is what give
this process its syntheticvalue.
 The name aldol condensation is also commonly
used,especially in biochemistry,to refer to just the first
stageof the process thealdol reaction itself as catalysed by
aldolases.

13. APPLICATIONS OF ALDOL CONDENSATION
Synthesis and antitumor, antiviral evaluation of chiral spiropyrans.
Chemical and Enzymatic synthesis of Fructose Analogues.
Sequential aldol condensation for the synthesis of new Glycine
antagonists.
Synthesis and biological evaluation of condensed pyridine and
condensed pyrimidine based HMG-CoA reductase inhibitors.
Stereo selective allyl transfer to chiral α-methoxy carbaldehydes.