chapter 8 aromaticity reactions of benzene and substituted benzenes 1
TRANSCRIPT
Chapter 8
Aromaticity
Reactions of Benzene and
Substituted Benzenes
1
The first structure for benzene was
proposed by August Kekulé in 1872.
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3
We often represent benzene as a hybrid of two equivalent structures
4
To name a benzene ring with one substituent, name the substituent and add the word benzene.
Naming Benzene Compounds
5
Common Names
OMe CH3 OH NH2
anisole toluene phenol aniline
CHO COOH CNstyrene benzaldehyde benzoic acid benzonitrile
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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
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• 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.
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10
Name the following benzene compounds.
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More practice…..Page 226 Problem 26
Page 214 Problem 14
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More naming…..
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Interesting Aromatic Compounds
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15
Reactions of Benzene: Oxidation
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What are the products of oxidation of the following compounds?
Another problem…..Page 213 Problem 12
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Side Chain Bromination
Reaction of an alkylbenzene with N-bromo-succinimide (NBS) and benzoyl peroxide (radical initiator) introduces Br into the side chain.
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Reduction of Aromatic Compounds
Reactions of Benzene: Electrophilic Substitution Vs Electrophilic Addition
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Electrophilic Aromatic Substitution
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22
Halogenation
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Nitration and Sulfonation
24
Friedel-Crafts Alkylation
25
Limitations of Friedel Crafts Reactions
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Page 212 Problem 11
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Friedel-Crafts Acylation
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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
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-OCH3 is ortho-para directing
Ortho-para Directors
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Meta Directors
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Types of Substituents
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Page 218 Problem 18
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Page 221 Problem 19
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Trisubstituted Benzenes
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Where would the electrophile attack the ring preferentially?
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Predict the major product of each of the following reactions.
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Synthesis of p-Bromobenzoic acid
40
The order of steps is important.
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