Bài giảng hóa hữu cơ phản ứng của arene

11.10
11.10
Reactions of Arenes:
Reactions of Arenes:
A Preview
A Preview
1. Some reactions involve the ring.
1. Some reactions involve the ring.
2. In other reactions the ring is a substituent.
2. In other reactions the ring is a substituent.
a) Reduction
a) Reduction
Catalytic hydrogenation (Section 11.4)
Catalytic hydrogenation (Section 11.4)
Birch reduction (Section 11.11)
Birch reduction (Section 11.11)
b) Electrophilic aromatic substitution
b) Electrophilic aromatic substitution
(Chapter 12)
(Chapter 12)
c) Nucleophilic aromatic substitution
c) Nucleophilic aromatic substitution
(Chapter 23)
(Chapter 23)
1. Reactions involving the ring
1. Reactions involving the ring
2. The ring as a substituent (Sections 11.12
2. The ring as a substituent (Sections 11.12
-
-
11.17)

11.17)
catalytic
catalytic
hydrogenation
hydrogenation
(Section 11.4)
(Section 11.4)
Birch reduction
Birch reduction
(Section 11.11)
(Section 11.11)

H
H
H
H
H
H
H
H
H
H
H
H
H
H

H
H
H

H
H
H
H
H
H
H
H
H
H
H
Reduction of Benzene Rings
Reduction of Benzene Rings

H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H

H
H
H
H
H
H
H
H
11.11
The Birch Reduction
(80%)
(80%)

H
H
H
H
H
H
H
H
H
H
H
H
H
H

H
H

H
H
H
H
H
H
H
H
H
H
H
H
Na, NH
Na, NH
3
3
CH
CH
3
3
OH
OH
Birch Reduction of Benzene
Birch Reduction of Benzene
Product is non
Product is non
-
-
conjugated diene.
conjugated diene.

Reaction stops here. There is no further reduction.
Reaction stops here. There is no further reduction.
Reaction is not hydrogenation. H
Reaction is not hydrogenation. H
22
is not involved in any way.
is not involved in any way.

H
H
H
H
H
H
H
H
H
H
H
H
Step 1: Electron transfer from sodium
Step 1: Electron transfer from sodium
+
+
Na
Na•
•
+
+
Na

Na
+
+
Mechanism of the Birch Reduction (Figure 11.8)
Mechanism of the Birch Reduction (Figure 11.8)
H
H
H
H

H
H
H
H
H
H
H
H
•
•
••
••
–
–
Step 2: Proton transfer from methanol
Step 2: Proton transfer from methanol
Mechanism of the Birch Reduction (Figure 11.8)
Mechanism of the Birch Reduction (Figure 11.8)
H
H

H
H

H
H
H
H
H
H
H
H
–
–
•
•
••
••
OCH
OCH
3
3
H
H
••
••
•
•
•
•

Step 2: Proton transfer from methanol
Step 2: Proton transfer from methanol
Mechanism of the Birch Reduction (Figure 11.8)
Mechanism of the Birch Reduction (Figure 11.8)
H
H
H
H

H
H
H
H
H
H
H
H
–
–
•
•
••
••
OCH
OCH
3
3
H
H

••
••
•
•
•
•



H
H
H
H
H
H
H
H
H
H
H
H
H
H
•
•
OCH
OCH
3
3
••

••
•
•
•
•
••
••
–
–
Step 3: Electron transfer from sodium
Step 3: Electron transfer from sodium
Mechanism of the Birch Reduction (Figure 11.8)
Mechanism of the Birch Reduction (Figure 11.8)

H
H
H
H
H
H
H
H
H
H
H
H
H
H
•
•

+
+
Na
Na•
•
Step 3: Electron transfer from sodium
Step 3: Electron transfer from sodium
Mechanism of the Birch Reduction (Figure 11.8)
Mechanism of the Birch Reduction (Figure 11.8)

H
H
H
H
H
H
H
H
H
H
H
H
H
H
•
•
+
+
Na
Na•

•

H
H
H
H
H
H
H
H
H
H
H
H
H
H
••
••
+
+
Na
Na
+
+
–
–
Step 4: Proton transfer from methanol
Step 4: Proton transfer from methanol
Mechanism of the Birch Reduction (Figure 11.8)
Mechanism of the Birch Reduction (Figure 11.8)

H
H
H
H
H
H
H
H
H
H
H
H
H
H
••
••
–
–
•
•
OCH
OCH
3
3
H
H
••
••
•

•

Step 4: Proton transfer from methanol
Step 4: Proton transfer from methanol
Mechanism of the Birch Reduction (Figure 11.8)
Mechanism of the Birch Reduction (Figure 11.8)

H
H
H
H
H
H
H
H
H
H
H
H
H
H
••
••
–
–
•
•
OCH
OCH
3

3
H
H
••
••
•
•
H
H

H
H
H
H
H
H
H
H
H
H
H
H
H
H
–
–
•
•
OCH
OCH

3
3
••
••
•
•
••
••

(86%)
(86%)

H
H
H
H
H
H
C(CH
C(CH
3
3
)
)
3
3
H
H
H
H

H
H

H
H
H
H
H
H
C(CH
C(CH
3
3
)
)
3
3
H
H
H
H
H
H
Na, NH
Na, NH
3
3
CH
CH
3

3
O
O
H
H
Birch Reduction of an Alkylbenzene
Birch Reduction of an Alkylbenzene
If an alkyl group is present on the ring, it ends up as
If an alkyl group is present on the ring, it ends up as
a substituent on the double bond.
a substituent on the double bond.