Electrophilic Aromatic Substitution

⚗️ Electrophilic Aromatic Substitution

Part 1 of 7 — EAS Mechanism

1. EAS

electrophile attacks aromatic ring → substitution product

2. Step 1

electrophilic attack → arenium ion (σ complex)

3. Step 2

deprotonation restores aromaticity

4. Aromaticity is preserved throughout

Aromaticity is preserved throughout

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Key Concepts Summary

• EAS: electrophile attacks aromatic ring → substitution product
• Step 1: electrophilic attack → arenium ion (σ complex)
• Step 2: deprotonation restores aromaticity
• Aromaticity is preserved throughout

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Halogenation & Nitration

Part 2 of 7 — Halogenation & Nitration

1. Halogenation

Ar-H + X₂/FeX₃ → Ar-X + HX

2. Nitration

Ar-H + HNO₃/H₂SO₄ → Ar-NO₂ + H₂O

3. Sulfonation

Ar-H + SO₃/H₂SO₄ → Ar-SO₃H

4. Lewis acid catalysts generate strong electrophiles

Lewis acid catalysts generate strong electrophiles

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Key Concepts Summary

• Halogenation: Ar-H + X₂/FeX₃ → Ar-X + HX
• Nitration: Ar-H + HNO₃/H₂SO₄ → Ar-NO₂ + H₂O
• Sulfonation: Ar-H + SO₃/H₂SO₄ → Ar-SO₃H
• Lewis acid catalysts generate strong electrophiles

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Friedel-Crafts Reactions

Part 3 of 7 — Friedel-Crafts Reactions

1. Friedel-Crafts alkylation

Ar-H + RCl/AlCl₃ → Ar-R

2. Friedel-Crafts acylation

Ar-H + RCOCl/AlCl₃ → Ar-COR

3. Acylation avoids rearrangement and polyalkylation

Acylation avoids rearrangement and polyalkylation

4. Deactivated rings don't undergo Friedel-Crafts reactions

Deactivated rings don't undergo Friedel-Crafts reactions

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Key Concepts Summary

• Friedel-Crafts alkylation: Ar-H + RCl/AlCl₃ → Ar-R
• Friedel-Crafts acylation: Ar-H + RCOCl/AlCl₃ → Ar-COR
• Acylation avoids rearrangement and polyalkylation
• Deactivated rings don't undergo Friedel-Crafts reactions

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Substituent Effects

Part 4 of 7 — Substituent Effects

1. Activating groups

EDG (donate electrons, speed up EAS)

2. Deactivating groups

EWG (withdraw electrons, slow down EAS)

3. ortho/para directors

-OH, -NH₂, -OR, -R, halogens

4. meta directors

-NO₂, -CN, -COOH, -COR, -SO₃H

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Key Concepts Summary

• Activating groups: EDG (donate electrons, speed up EAS)
• Deactivating groups: EWG (withdraw electrons, slow down EAS)
• ortho/para directors: -OH, -NH₂, -OR, -R, halogens
• meta directors: -NO₂, -CN, -COOH, -COR, -SO₃H

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Multi-Step EAS

Part 5 of 7 — Multi-Step EAS

1. Order of reactions matters for desired product

Order of reactions matters for desired product

2. Blocking groups can be used strategically

Blocking groups can be used strategically

3. Retrosynthetic analysis for multi-step EAS

Retrosynthetic analysis for multi-step EAS

4. Clemmensen/Wolff-Kishner reduction

Ar-COR → Ar-CH₂R

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Key Concepts Summary

• Order of reactions matters for desired product
• Blocking groups can be used strategically
• Retrosynthetic analysis for multi-step EAS
• Clemmensen/Wolff-Kishner reduction: Ar-COR → Ar-CH₂R

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Problem-Solving Workshop

Part 6 of 7 — Problem-Solving Workshop

1. Predicting EAS products with directing effects

Predicting EAS products with directing effects

2. Drawing EAS mechanisms

Drawing EAS mechanisms

3. Designing multi-step aromatic syntheses

Designing multi-step aromatic syntheses

4. Analyzing substituent effects on reactivity

Analyzing substituent effects on reactivity

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Key Concepts Summary

• Predicting EAS products with directing effects
• Drawing EAS mechanisms
• Designing multi-step aromatic syntheses
• Analyzing substituent effects on reactivity

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Synthesis & Review

Part 7 of 7 — Synthesis & Review

1. EAS is the primary reaction of aromatic compounds

EAS is the primary reaction of aromatic compounds

2. Directing effects control regiochemistry

Directing effects control regiochemistry

3. Multi-step synthesis requires planning

Multi-step synthesis requires planning

4. Review

EAS reactions and directing groups

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Key Concepts Summary

• EAS is the primary reaction of aromatic compounds
• Directing effects control regiochemistry
• Multi-step synthesis requires planning
• Review: EAS reactions and directing groups

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