CH 19 Reactions
CHM 2211
Preparation of Aldehydes
H
PCC
OH
Mild oxidizing agent, PCC will oxidize primary
alcohols to aldehydes but will not oxidize alkenes
O
CH2Cl2
O
O3
O
using cyclic alkenes a dicarbonyl cmpd results
H
Zn, CH3 CO2 H
O
O3
O
H
Zn, CH3CO2H
H
O
O
O3
H
Zn, CH3 CO2 H
O
+
H
using alkenes with at least 1
vinylic hydrogen, oxidative cleavage
results in aldehydes
O
H
DIBAH toluene
O
-78 C
H3 O+
H
DIBAH =
Al
Preparation of Ketones
OH
O
PCC
Several oxidizing agents can be used (see CH 17)
to produce ketones from secondary alcohols
CH2Cl2
O3
H 2C O
+
Zn, H3O+
O
ozonolysis produces ketones if one of the
unsaturated carbon atoms is disubstituted
O
O
+
AlCl3
Cl
Friedel Craft's Acylation
heat
H3O+
methyl ketones are produced by hydration of
terminal alkynes
HgSO4
O
Cl
O
(CH3)2CuLi
ether
O
1
Oxidation of Aldehydes and Ketones
Oxidation of an aldehyde to a carboxylic acid can be accomplished by several reagents
Jones reagent = CrO3, H3O+, acetone, 0C
Tollens reagent = Ag2O, NH4OH, H2O
Oxidations of ketones are much more difficult to accomplish
Oxidative Cleavage with KMnO4, H2O, NaOH, H3O+
Nucleophilic Addition Reactions
Nucleophile can be negatively charged
HO-, H-, R3C-, RO-, NCNucleophile can be neutral
H2O, ROH, NH3, RNH2
Base catalyzed hydration of aldehyde/ketone
O
NaOH
OH
H2O
+
NaOH
+
NaOH
OH
O
NaOH
H
H2O
OH
H
OH
Acid catalyzed hydration of aldehyde/ketone
2
OH
H3O+
O
+
H2O
OH
OH
H3O+
O
H2O
H
H3O+
H
+
H3O+
OH
Addition of H-Y to C=O Y = electronegative
Y
+
Y = -OCH3, -OH, -Br, -Cl, HSO4-
H-Y
OH
O
Cyanohydrin Formation
CN
+
HCN
OH
O
Aldehydes and unhindered ketones
Cyanohydrin reactions
CN
OH
CN
LiAlH4
THF
H2O
H3O+
heat
OH
CH2NH2
forms a primary amine
OH
COOH
forms carboxylic acids
OH
Addition of Grignard Reagents
3
CH2CH3
CH3CH2MgX
ether
O
H3O+
OH
aldehyde or ketone
Hydride Addition
LiAlH4 or NaBH4
O
+
ethanol H3O+
H2O
OH
aldehyde or ketone
Addition of Amines (Imine and Enamine formation)
Add. Of primary amines leads to imines
O
N
CH3CH2CH2NH2
H3O+
H
CH2CH2CH3
H
+
H3O+
+
H3O+
aldehyde or ketone
Add. Of secondary amines leads to enamines
O
H
H3C
(CH3)2NH
H3O+
H
N
CH3
aldehyde or ketone
Addition of Hydrazine: W-K reaction
4
H2NNH2
O
H3O+
+
KOH
-OH
yields an alkane
aldehyde or ketone
Addition of Alcohols (acetal formation)
O
2 CH3CH2OH
HCl
OCH2CH3
+
H2O
OCH2CH3
aldehyde or ketone
Addition of Phosphorus Ylides: Wittig Reaction
O
(CH3)2C-P+(Ph)3
THF
+
O=P(Ph)3
aldehyde or ketone
Cannizaro Reaction
Addition to ,-unsaturated Aldehydes and Ketones
5
Conjugate Addition of Amines
O
CH3NH2
O
NHCH3
H3O+
aldehyde or ketone
Conjugate Addition of Alkyl groups: Organocopper Reactions
O
(CH3)2CuLi
ether
H3O+
O
CH3
ketone only
6