Some reactions involve the ring.. In other reactions the ring is a substituent... a ReductionCatalytic hydrogenation Section 11.4 Birch reduction Section 11.11 b Electrophilic aromatic s
Trang 111.10 Reactions of Arenes:
A Preview
1 Some reactions involve the ring
2 In other reactions the ring is a substituent
Trang 2a) Reduction
Catalytic hydrogenation (Section 11.4) Birch reduction (Section 11.11)
b) Electrophilic aromatic substitution
(Chapter 12) c) Nucleophilic aromatic substitution
(Chapter 23)
1 Reactions involving the ring
2 The ring as a substituent (Sections 11.12-11.17)
Trang 3catalytic
hydrogenation
(Section 11.4)
Birch reduction (Section 11.11) H
H
H H
H
H
Reduction of Benzene Rings
H H
H
H
H
H H
H
Trang 411.11 The Birch Reduction
Trang 5H
H
H H
H
H
Na, NH3
CH3OH
Birch Reduction of Benzene
Product is non-conjugated diene.
Reaction stops here There is no further reduction.
Trang 6H
H H
Step 1: Electron transfer from sodium
Mechanism of the Birch Reduction (Figure 11.8)
H
H
H
H
H
H
•
••
–
Trang 7Step 2: Proton transfer from methanol
Mechanism of the Birch Reduction (Figure 11.8)
H
H
H
H
H
H
–
•
••
OCH3
H
••
•
•
Trang 8Step 2: Proton transfer from methanol
Mechanism of the Birch Reduction (Figure 11.8)
H
H
H
H
H
H
–
•
••
OCH3
H
••
•
•
H
H
H
H
H H
H
•
OCH3
••
•
• ••
–
Trang 9Step 3: Electron transfer from sodium
Mechanism of the Birch Reduction (Figure 11.8)
H
H
H
H
H H
H
•
+ •Na
Trang 10Step 3: Electron transfer from sodium
Mechanism of the Birch Reduction (Figure 11.8)
H
H
H
H
H H
H
•
+ •Na
H
H
H
H
H H
H
••
+ Na+ –
Trang 11Step 4: Proton transfer from methanol
Mechanism of the Birch Reduction (Figure 11.8)
H
H
H
H
H H
H
••
–
• OCH3 H
••
•
Trang 12Step 4: Proton transfer from methanol
Mechanism of the Birch Reduction (Figure 11.8)
H
H
H
H
H H
H
••
–
• OCH3 H
••
•
H
H
–
• OCH3
••
•
••
Trang 13H
H
H H
H
H
Na, NH3
CH3OH
Birch Reduction of an Alkylbenzene
If an alkyl group is present on the ring, it ends up as
a substituent on the double bond