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SECTION 15 ² ELECTROPHILIC AROMATIC SUBSTITUTION...

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Page 1: SECTION 15 ² ELECTROPHILIC AROMATIC SUBSTITUTION …ochemnotes.com/section15-electrophilic-aromatic-substitution.pdf · SECTION 15 ² ELECTROPHILIC AROMATIC SUBSTITUTION ... Overview

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SECTION 15 ELECTROPHILIC AROMATIC SUBSTITUTION

15-1 -- The Chemistry of Benzene (C6H6)

15-1 -- General Mechanism of Electrophilic Aromatic Substitution (E.A.S.)

Delocalization of Charge

An Addition Reaction is Not Observed

15-2 -- Overview of Electrophilic Aromatic Substitution Reactions

Nitration (Adding NO2 to the Benzene Ring)

Sulfonation (Adding SO3H to the Benzene Ring)

Halogenation (Adding -X to the Benzene Ring)

Friedel-Crafts Alkylation (Adding -R to the Benzene Ring)

Friedel-Crafts Acylation (Adding -COR to the Benzene Ring)

15-3 -- The Nitration Reaction

Detailed Mechanism

Product is Nitrobenzene

15-3 -- The Sulfonation Reaction

Product is Benzenesulfonic Acid

Detailed Mechanism

Use of Fuming Sulfuric Acid

Le Chatelier s Principle and Possible Desulfonation

Principle of Microscopic Reversibility

15-5 -- Halogenation of Aromatic Rings

Product is a Halobenzene

Use of the Lewis Acid Catalyst, FeCl3

Detailed Mechanism

Iodination Mechanism is a Bit Different (CuCl2 as Catalyst)

15-6 -- Friedel-Crafts Alkylation

Doesn t Proceed on Aromatic Rings with Strongly Deactivating Substituents

Detailed Mechanism Works Well with R-Cl, R-Br, R-I, or R-F

Rearrangements of R and the Involvement of Free Carbocations

15-8 -- Friedel-Crafts Acylation

The Acyl Group

Detailed Mechanism

The Acylium Ion Not Prone to Rearrangement

15-9 -- Use H+ (D+) as the Electrophile

15-10 -- Directing Effects of Substituents

Ortho (o), Meta (m), and Para (p) Directors

Activators vs. Deactivators

Mechanism of Para Attack by an Electrophile

Page 2: SECTION 15 ² ELECTROPHILIC AROMATIC SUBSTITUTION …ochemnotes.com/section15-electrophilic-aromatic-substitution.pdf · SECTION 15 ² ELECTROPHILIC AROMATIC SUBSTITUTION ... Overview

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Mechanism of Ortho Attack by an Electrophile

Mechanism of Meta Attack by an Electrophile

15-11 -- More on Activating, o,p-Directoring Groups

Electron-Withdrawing Induction vs. Resonance

15-13 -- More on Deactivating, m-Directoring Groups

15-13 -- Halogens are o,p-Directors and Weak Activators

15-14 -- Detailed Summary of Substituents Directing Effects

Activating, o,p-Directors (Both Strong and Weak)

Deactivatinig, m-Directors (Both Strong and Weak)

Deactivating, o,p-Directors (Weak)

15-14 -- Miscellaneous Notes About E.A.S Reactions

Important Side Notes on Friedel-Crafts Reactions

Ortho-Para Product Ratio is Sensitive to Steric Effects

Important Substituent Transformations (i.e. NO2 converted to NH2)

What if 2 or More Substituents Directing Effects Oppose Each Other?

15-17 -- Organic Synthesis of Benzene Derivatives

The Order of Reactions is Critical

15-18 -- Nucleophilic Aromatic Substitution Reactions (N.A.S.)

Mechanism #1: Addition-Elimination

Meisenheimer Complex

Need a Good Leaving Group (l.g.) and an Electron-Withdrawing Group

Mechanism #2: Elimination-Addition

Occurs via Benzyne Mechanism

Need a Very Strong Base

15-21 -- Benzyne Can Act as a Dienophile and React with Dienes

15-22 -- Side-Chain Oxidation Reactions (Use of KMnO4)

15-22 -- Benzylic Bromination Reactions

Occurs via a Free Radical Chain Mechanism

NBS = N-Bromosuccinimide

Page 3: SECTION 15 ² ELECTROPHILIC AROMATIC SUBSTITUTION …ochemnotes.com/section15-electrophilic-aromatic-substitution.pdf · SECTION 15 ² ELECTROPHILIC AROMATIC SUBSTITUTION ... Overview
Page 4: SECTION 15 ² ELECTROPHILIC AROMATIC SUBSTITUTION …ochemnotes.com/section15-electrophilic-aromatic-substitution.pdf · SECTION 15 ² ELECTROPHILIC AROMATIC SUBSTITUTION ... Overview
Page 5: SECTION 15 ² ELECTROPHILIC AROMATIC SUBSTITUTION …ochemnotes.com/section15-electrophilic-aromatic-substitution.pdf · SECTION 15 ² ELECTROPHILIC AROMATIC SUBSTITUTION ... Overview
Page 6: SECTION 15 ² ELECTROPHILIC AROMATIC SUBSTITUTION …ochemnotes.com/section15-electrophilic-aromatic-substitution.pdf · SECTION 15 ² ELECTROPHILIC AROMATIC SUBSTITUTION ... Overview
Page 7: SECTION 15 ² ELECTROPHILIC AROMATIC SUBSTITUTION …ochemnotes.com/section15-electrophilic-aromatic-substitution.pdf · SECTION 15 ² ELECTROPHILIC AROMATIC SUBSTITUTION ... Overview
Page 8: SECTION 15 ² ELECTROPHILIC AROMATIC SUBSTITUTION …ochemnotes.com/section15-electrophilic-aromatic-substitution.pdf · SECTION 15 ² ELECTROPHILIC AROMATIC SUBSTITUTION ... Overview
Page 9: SECTION 15 ² ELECTROPHILIC AROMATIC SUBSTITUTION …ochemnotes.com/section15-electrophilic-aromatic-substitution.pdf · SECTION 15 ² ELECTROPHILIC AROMATIC SUBSTITUTION ... Overview
Page 10: SECTION 15 ² ELECTROPHILIC AROMATIC SUBSTITUTION …ochemnotes.com/section15-electrophilic-aromatic-substitution.pdf · SECTION 15 ² ELECTROPHILIC AROMATIC SUBSTITUTION ... Overview
Page 11: SECTION 15 ² ELECTROPHILIC AROMATIC SUBSTITUTION …ochemnotes.com/section15-electrophilic-aromatic-substitution.pdf · SECTION 15 ² ELECTROPHILIC AROMATIC SUBSTITUTION ... Overview
Page 12: SECTION 15 ² ELECTROPHILIC AROMATIC SUBSTITUTION …ochemnotes.com/section15-electrophilic-aromatic-substitution.pdf · SECTION 15 ² ELECTROPHILIC AROMATIC SUBSTITUTION ... Overview
Page 13: SECTION 15 ² ELECTROPHILIC AROMATIC SUBSTITUTION …ochemnotes.com/section15-electrophilic-aromatic-substitution.pdf · SECTION 15 ² ELECTROPHILIC AROMATIC SUBSTITUTION ... Overview

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SECTION 15 – ELECTROPHILIC AROMATIC SUBSTITUTION

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