www.OChemNotes.com

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

www.OChemNotes.com

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

www.OChemNotes.com

SECTION 15 – ELECTROPHILIC AROMATIC SUBSTITUTION

Were the FREE Section 15 Notes Useful? Want the FULL VERSION of the Section 15 Notes?

Download Them Instantly for Only $6.99 at:

OChemNotes.com