An Enol Is a Better Nucleophile
Than an Alkene
Question
•  Which compound is the aldol addition product
of pentanal (CH3CH2CH2CH2CHO)?
•  A)
B)
•  C)
D)
Question
•  Which compound is the aldol addition product
of propanal when the reaction is carried out
at 80 - 100°C?
• 
A)
B)
• 
C)
D)
Intramolecular Aldol Additions
Question
•  The intramolecular aldol addition of 1,5-cyclononanedione
on the right
@ 100 oC will produce:
•  A)
B)
•  C)
D)
One product will be formed if one of the carbonyl
compounds does not have any α-hydrogen
Biochemical Aldol Condensation
An Enol Is a Better Nucleophile
Than an Alkene
An Acid-Catalyzed
α-Substitution Reaction
A Base-Catalyzed
α-Substitution Reaction
Using LDA (lithium diisopropyl amide)
to form enolate
Lithium diisopropylamide
Ketone Enolates
Alkylation of the α-Carbon of
Carbonyl Compounds
Question
•  What is the product isolated when butanal is
treated with LDA followed by addition of ethyl
bromide?
Unsymmetrical Ketones
•  A)
B)
•  C)
D)
Regioselectivity
+Li
Bu-
Enamines react as enolates
(Under much milder conditions)
Aldehydes and ketones can be acylated via enamines
Selectivity
NOTE: alkylation of an aldehyde or a ketone using
an enamine yields the monoalkylated product
Acid-Catalyzed Halogenation
An α-hydrogen is substituted with a bromine
Base Halogenation
Conversion of a Methyl Ketone to a
Carboxylic Acid
Under basic conditions, all of the α-hydrogens are
substituted for bromines
Halogenation of the α-Carbon of
Carboxylic Acids
When the α-carbon is halogenated, the halogen can serve
as a leaving group
If a bulky base is used, an E2 elimination will occur