Chapter 8
Aromaticity
Reactions of Benzene and
Substituted Benzenes
1
The first structure for benzene was
proposed by August Kekulé in 1872.
2
3
We often represent benzene as a hybrid of two equivalent
structures
4
Naming Benzene Compounds
To name a benzene ring with one substituent, name the
substituent and add the word benzene.
5
Common Names
OMe
anisole
styrene
CH3
OH
toluene
phenol
CHO
COOH
benzaldehyde
benzoic acid
NH2
aniline
CN
benzonitrile
6
ortho-dibromobenzene
or
o-dibromobenzene
or 1,2-dibromobenzene
meta-dibromobenzene
or
m-dibromobenzene
or 1,3-dibromobenzene
para-dibromobenzene
or
p-dibromobenzene
or 1,4-dibromobenzene
7
• If the two groups on the benzene ring are different,
alphabetize the names of the substituents preceding the
word benzene.
• If one substituent is part of a common root, name the
molecule as a derivative of that monosubstituted
benzene.
8
For three or more substituents on a benzene ring:
1. Number to give the lowest possible numbers around the ring.
2. Alphabetize the substituent names.
3. When substituents are part of common roots, name the
molecule as a derivative of that monosubstituted benzene. The
substituent that comprises the common root is located at C1.
9
10
Name the following benzene compounds.
11
Page 214 Problem 14
More practice…..
Page 226 Problem 26
12
More naming…..
13
Interesting Aromatic Compounds
14
15
Reactions of Benzene: Oxidation
16
What are the products of oxidation of the
following compounds?
Another problem…..Page 213 Problem 12
17
Side Chain Bromination
Reaction of an alkylbenzene with N-bromo-succinimide
(NBS) and benzoyl peroxide (radical initiator)
introduces Br into the side chain.
18
Reduction of Aromatic Compounds
19
Reactions of Benzene: Electrophilic
Substitution Vs Electrophilic Addition
20
Electrophilic Aromatic Substitution
21
22
Halogenation
23
Nitration and Sulfonation
24
Friedel-Crafts Alkylation
25
Limitations of Friedel Crafts Reactions
26
Page 212 Problem 11
27
Friedel-Crafts Acylation
28
Di- and Polysubstitution


Existing groups on a benzene ring influence
further substitution in both orientation and rate
Orientation


certain substituents direct new substitution
preferentially toward ortho-para positions, others
direct preferentially toward meta positions
Rate

certain substituents are activating toward further
substitution, others are deactivating toward further
substitution
29
Ortho-para Directors
-OCH3 is ortho-para directing
30
Meta Directors
31
Types of Substituents
32
Page 218 Problem 18
33
Page 221 Problem 19
34
Trisubstituted Benzenes
35
36
37
Where would the electrophile attack the
ring preferentially?
38
Predict the major product of each of the
following reactions.
39
Synthesis of p-Bromobenzoic acid
40
The order of steps is important.
41