aldehyde-ketone- 1.ppt
TRANSCRIPT
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Aldehydes and Ketones
Nucleophilic Addition to the Carbonyl Group1
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IUPAC Nomenclature of Aldehydes
1) Base the name on the chain that contains the carbonyl group and replace the -e ending of the hydrocarbon by -al.
4,4-dimethylpentanal
5-hexenal
2-phenylpropanedial
(keep the -e ending
before -dial)H
O
O
H
O
O
HCCHCH
4
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IUPAC Nomenclature of Aldehydes
2. The aldehyde functional group has priority over
-X, -OH, -OR, double and triple bonds.
Name OH as hydroxy substituent
Name OR as alkoxy substituent
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1) Base the name on the chain that contains the carbonyl group and replace -e by -one. Number the chain in the direction that gives the lowest number to the carbonyl carbon.
Substitutive IUPAC Nomenclature of Ketones
3-hexanone
4-methylcyclohexanone
4-methyl-2-pentanone
O
CH3CH2CCH2CH2CH3
O
CH3CHCH2CCH3
CH3
H3C
O
6
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Trivial name for common aldehydes and ketones are widely used. Aldehydes are named after the parent carboxylic acids with oic acid or ic acid ending changed to aldehyde
Propanone is usually called acetone, while the other simple ketones are sometimes named by a functional-group name. The alkyl or aryl groups attached to the carbonyl group are named, then the word ketone is added.
1.unknown - 2.unknown
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Other positions in a molecule in relation to the carbonyl group may be referred to be Greek letters
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boiling point
6C
49C
97C
Aldehydes and ketones have higher boiling
than alkenes, but lower boiling points than alcohols.More polar than alkenes, but cannot form intermolecular hydrogen bonds to other carbonyl groups
O
OH
12
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from alkenes
ozonolysis
from alkynes
hydration (via enol)
from arenes
Friedel-Crafts acylation
from alcohols
oxidation
Synthesis of Aldehydes and Ketones
A number of
reactions already
studied provide
efficient synthetic
routes to
aldehydes and
ketones.17
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nucleophiles attack carbon;
electrophiles attack oxygenResonance Description of
Carbonyl GroupC
O
C
O
+
12
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Acid Catalyst Makes Carbon More Electrophilic
Step 1:
+
+
H
C
OH
+
C
O
H
O
H
H
+
C
OH
+
H
O
-
Nucleophilic
Addition to Carbonyl Groups
Basic ReactionC
O
Nu
C
O
Nu:
-
Ketones are Less Reactive Than Aldehydes
Steric Reasons
R Groups are more electron donating than H
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Nucleophiles
Group IV Nucleophiles
(CN)-Grignard ReagentsOrganolithium CompoundsAcetylide IonGroup V Nucleophiles
Ammonia; NH3Primary Amines; NH2RSecondary Amines; NHR23.unknown -
Nucleophiles (cont)
Group VI Nucleophiles
Water; H2OHydroxide Ion; (OH)-Alcohol; ROH(OR)-Group I Nucleophiles
Hydride Ion; :H-LiAlH4NaBH4Phosphourous Ylide
(C6H5)3P
C
+
A
B
(C6H5)3P
C
A
B
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Types of Reactions
Nucleophilic Addition in Basic Medium
Group IV Nu
Group I Nu
Two Nu; Nucleophilic Addition/ Elimination of Water(Acidic Medium)
2 Nu Substitute; Elimination of Water
Group VI Nu1 Nu Substitute; 1 Base Abstract H; Elimination of Water
Group V Nu
Nucleophilic Addition/ Elimination
Phosphorous Ylide
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Nucleophilic Addition in Basic Medium
Group IV Nu & Group I NuMechanism
Nucleophilic Attack to Electrophilic Carbon
Protonation
Group IV Nucleophiles
(CN)-Grignard ReagentsOrganolithium CompoundsAcetylide IonGroup I Nucleophiles
Hydride Ion; :H-LiAlH4NaBH44.unknown -
Cyanohydrin Formation
NET REACTION
C
O
H
C
O
N
C
+
HCN
18
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Example
Cl
Cl
CH
O
Cl
Cl
CHCN
OH
NaCN, water
then H2SO4
O
CH3CCH3
OH
CH3CCH3
CN
NaCN, water
then H2SO4
20
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Cyanohydrin Formation
Step 1; Nucleophilic Attack
C
O
N
C
18
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Cyanohydrin Formation
Step 2: Protonation to form OH group.
O
N
C
C
H
H
+
O
H
H
H
O
O
N
C
C
H
18
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Acetylide Ion as a Nucleophile
+
2. H3O+
(65-75%)
1. Form Nucleophile by removing weakly acidic H.
2. Nucleophilic Addition Reaction.
HC
CH
HC
CNa
NaNH2
NH3
HC
C:-
O
CH
C
HO
-
Grignard reagents act as nucleophiles
toward the carbonyl groupC
O
+
two-step sequence gives an alcohol as the isolated product
R
MgX
C
R
MgX
+
O
diethyl
etherC
R
OH
H3O+
-
Examples
+
CH3(CH2)4CH2MgBr
+
2) H3O+
MgCl
C
O
H
H
CH2OH
H3O
2)
C
O
H3C
H
CH3(CH2)4CH2CHCH3
OH
-
OrganoLithium Compounds react like Grignard Reagents
(76%)
+
1. diethyl ether
2. H3O+
H2C
CHLi
O
CH
CH2
CHCH
OH
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Reduction Reactions
Reducing Agents; LiAlH4 , NaBH4Examples
5.unknown -
Retrosynthetic Analysis of Alcohols
Step 1 Locate the carbon that bears the hydroxyl group.
Step 2 Disconnect one of the groups attached to this carbon
C
OH
C
OH
15
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Retrosynthetic Analysis of Alcohols
What remains is the combination of Grignard reagent and carbonyl compound that can be used to prepare the alcohol.
C
O
MgX
15
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Example
CH3MgX
There are two other possibilities.
Can you see them?C
OH
CH3
CH2CH3
O
C
CH2CH3
20
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Synthesis
1.
2. H3O+
CH3Br
Mg, diethyl ether
CH3MgBr
C
OH
CH3
CH2CH3
O
C
CH2CH3
21
C
H
3
C
C
H
3
O
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C-R
-
CH
3
CH
2
C
CH
2
CH
3
O
+ LiAlH
4
2) H
3
O
+
CH
3
CH
2
CH
CH
2
CH
3
OH