Fundamentals of Organic Chemistry
Chapter 16
Chemistry of Benzene:
Electrophilic Aromatic Substitution
Chemistry Department
Dr Emilia Oueis
CHEM211
McMurry. OrganicChemistry. Cengage. 2016
9th Intl. Ed. ISBN-10: 1305080483
SAN campus, BuHasa (Building 2), 2010
Office hours: MW 12:00-01:30 pm
emilia.oueis@ku.ac.ae
Chemistry of Benzene: Electrophilic Aromatic Substitution
Aromaticity: the stability associated with benzene and related
compounds that contain a cyclic conjugated system of 4n + 2 
electrons.
Electrophilic aromatic substitution: an electrophile (E+) reacts
with an aromatic ring and substitutes for one of the hydrogens.
E: a halogen (—Cl, —Br, —I),
a nitro group (— NO2), a sulfonic
acid group (—SO3H), a hydroxyl group (—OH), an alkyl
group (—R), or an acyl group (—COR)
16.1 Electrophilic Aromatic Substitution Reactions:
Bromination
electrophilic alkene additions
electrophilic aromatic substitution
carbocation intermediate
catalyst
FeBr3
Figure 16.1 A comparison of the reactions of an electrophile
(E+) with an alkene and with benzene
16.1 Electrophilic Aromatic Substitution Reactions:
Bromination
- stability of the aromatic ring
is retained,
- the overall process is exergonic.
16.1 Electrophilic Aromatic Substitution Reactions:
Bromination
16.2 Other Aromatic Substitutions
Aromatic Fluorination, Chlorination, and Iodination
16.2 Other Aromatic Substitutions
Aromatic Nitration
Aromatic Sulfonation
An electrostatic potential map of the
reactive electrophile NO2 shows that
the nitrogen atom is the most positive
An electrostatic potential map of the
reactive electrophile HOSO2 shows that
sulfur and hydrogen are the most
positive atoms
16.2 Other Aromatic Substitutions
16.3 Alkylation and Acylation of Aromatic Rings: The
Friedel–Crafts Reaction
alkylation—the introduction of an alkyl group onto the benzene ring.
limitations
16.3 Alkylation and Acylation of Aromatic Rings: The
Friedel–Crafts Reaction
limitations
16.3 Alkylation and Acylation of Aromatic Rings: The
Friedel–Crafts Reaction
Acylation reaction: a carboxylic acid chloride, RCOCl, in the presence of AlCl3 will react with benzene.
The electrophile is a resonance-stabilized
acyl cation, whose electrostatic potential
map indicates that carbon is the most
positive atom
Mechanism of the Friedel–Crafts acylation reaction
16.3 Alkylation and Acylation of Aromatic Rings: The
Friedel–Crafts Reaction
1. Study Questions for Problem Solving Sessions
From textbook (McMurry, 9th Edition) Chapter 16.
Questions: 1, 3, 5, 7, 36, 50 (a,b,c), 54 (a and c)
2. Reading Assignment
Textbook, Chapter 16 (1-3)