Ch.19 Aldehydes and Ketones
Ways to make an Aldehyde:
H
1.
O
OH
PCC
C
R
CH 2Cl 2
H
Primary Alcohol
2.
R
H
C
PCC = Oxidation = More bonds to Oxygen
R
R
O3
1.
H
C
C
H
2. Zn, CH 3COOH
R'
+
O
O
H
H
O 3 = Cutting the Double bond in half
(Must have a vinylic H to happen)
R'
*** Watch out for a cyclic alkene...
it becomes a dicarbonyl
C
Alkene
3.
O
O
1. DIBAH in toluene
R
2. H3O
OR'
+
C
+
R
R'OH
DIBA H = partial reduction
H
Ester
Ways to make a Ketone:
1. H
O
OH
PCC
C
R
R'
Secondary Alcohol
When you see anything with Cr, think oxidize
CH 2Cl 2
R
R'
O
O
2.
CH2
1.
O
O3
2. Zn / H 3O
CH3
+
+
CH3
Careful, the double bond still gets cut in half
to mak e 2 products
CH 2O
(Be sure its the double bond of the alk ene)
An alkene
O
O
3.
+R
AlCl 3
C
C
Hg
H
O
R
+
Cl
Acid chloride
2
+
H2SO 4, H2O
Alkyne
5.
Ch. 16: FC Acylation
Cl
4.
R
R
-
O
C
R
CH3
Hg = Hydration of alk ynes at the end of a chain
to mak e Methyl k etones
O
+
R'2CuLi
ether
Cl gets replaced by one R'
R
R'
Oxidizing Aldehydes:
O
1.
OH
R
R
H
O
CrO3
OH
H3O
Cr = More bonds with Oxygen
+
R
H
OH
hydrate
O
O
2.
Ag 2O
H
OH
Tollens reagent
+
NH 4OH, H 2O,
ethanol
Ag
Oxidizing Ketones:
1.
O
1. Hot KMnO4
H2O, NaOH
2. H3O
COOH
Works for symmetrical ketones
+
COOH
Nu-Addition Reactions of Aldehydes & Ketones:
O
O
R
OH
-
H
-
Nu
R
R
Nu
R'
Ketone or Aldehyde
+
R'
R'
-
Nu-H
O
Nu can either be negatively charged or neutral
R
R'
-
H
O
+
Nu
H
Nu
- H 2O
R
Nu-H
R'
Nu H
Trends for Ranking Problems:
In Nu- Addition reactions…
Stability =
Reactivity
Aldehydes > Ketones
More reactive Less reactive
Aldehydes:
Aliphatic > Aromatic
(Steric and Electronic Effects)
(Resonance effect)
R
R'
Nucleophilic Addition Reactions
1. Hydration
Base-catalyzed:
O
-
O
H
-
OH
R
R'
Aldehyde or Ketone
R
H
O
OH
R
R'
OH
R'
-
+
OH
OH
Acid-catalyzed:
+
O
OH
+
H O H
H
R'
R
OH
H2O
R
OH
R
R
O
H
+
R
+
R
H2O
+
OH
R
H
H3O
2. Cyanohydrin Formation:
O
-
-
C
O
HO
CN
N
HCN
H
H
CN
+ -C
H
N
3. Grignard Reagent:
MgX
+
O
R
H
+
O
-
MgX :R
:R
and ethe r
R
MgX
O
H3O
-
+ HOMgX
R
R
H
H
OH
+
R
-
H
R'
4. 1 Amines: Imine
R'
O
:NH2R'
R
H
O
-
OH
H
R
+
N H
H
R'
H transfer
H3O
H
R
H
N
R'
+
+
O
H
R'
+
N
H
H2O
H
R
H
R
N
R'
N
H
H
+ H3 O
R
H
Imine
+
5. 2  Amines: Enamine
O
H
C
OH
H
C
:NHR2
H
H
H
R2N
O
+
H
+
R
+
N
H
H
C
+
C
C
H
R
N
H2O
H
H
C
R
R
H
H3O
C
R2 N
Enamine
6. Wolff-Kishner (Hydrazine addition):
 To convert aldehydes and ketones into alkanes
O
H2NNH2
R
R'
H
H
+
C
KOH
R
+
N2
H2O
R'
7. Adding Alcohols: (Acetals)
O
+
R
Acid catalyst
2 R"OH
R"O
( i.e. HCl )
R'
OR"
R
+
H2O
R'
8. Wittig:
O
+
P(Ph) 3
C
C
R
-
O
C
R'
-
+
P(Ph) 3
O
P(Ph) 3
C
C
C
R'
R
R'
R
R'
C
+ (Ph)3P
C
R
O
+