Chapter 18
Reactions of Aromatic Compounds
NMR Spectroscopy of Benzene Derivatives
Simple unsubstituted benzene has six aromatic protons, all chemically equivalent. Therefore, benzene exhibits only a singlet peak at δ 7.3 ppm ...
Reactions at the Benzylic Position: Oxidation and Reduction
The benzylic position describes the position of a carbon atom attached directly to a benzene ring. Benzene by itself does not undergo oxidation. In ...
Reactions at the Benzylic Position: Halogenation
Benzylic halogenation takes place under conditions that favor radical reactions such as heat, light, or a free radical initiator like peroxide.
The ...
Electrophilic Aromatic Substitution: Overview
In an electrophilic aromatic substitution reaction, an electrophile substitutes for a hydrogen of an aromatic compound.
Many functional groups can be ...
Electrophilic Aromatic Substitution: Chlorination and Bromination of Benzene
Chlorination and bromination are important classes of electrophilic aromatic substitutions, where benzene reacts with chlorine or bromine in the presence ...
Electrophilic Aromatic Substitution: Fluorination and Iodination of Benzene
Bromination and chlorination of aromatic rings by electrophilic aromatic substitution reactions are easily achieved, but fluorination and iodination are ...
Electrophilic Aromatic Substitution: Nitration of Benzene
The nitration of benzene is an example of an electrophilic aromatic substitution reaction. It involves the formation of a very powerful electrophile, the ...
Electrophilic Aromatic Substitution: Sulfonation of Benzene
Sulfonation of benzene is a reaction wherein benzene is treated with fuming sulfuric acid at room temperature to produce benzenesulfonic acid. Fuming ...
Electrophilic Aromatic Substitution: Friedel–Crafts Alkylation of Benzene
Friedel–Crafts reactions were developed in 1877 by the French chemist Charles Friedel and the American chemist James Crafts. Friedel–Crafts ...
Electrophilic Aromatic Substitution: Friedel–Crafts Acylation of Benzene
The Friedel–Crafts acylation reactions involve the addition of an acyl group to an aromatic ring. These reactions proceed via electrophilic aromatic ...
Limitations of Friedel–Crafts Reactions
Several restrictions limit the use of Friedel–Crafts reactions. First, the halogen in the alkyl halide must be attached to an sp3-hybridized carbon ...
Directing Effect of Substituents: ortho–para-Directing Groups
Ortho–para directors are substituent groups attached to the benzene ring and direct the addition of an electrophile to the positions ortho or para ...
Directing Effect of Substituents: meta-Directing Groups
Substituents on the benzene ring that direct an incoming electrophile to undergo substitution at the meta position are ...
ortho–para-Directing Activators: –CH3, –OH, –NH2, –OCH3
All ortho–para directors, excluding halogens, are activating groups. These groups donate electrons to the ring, making the ring carbons ...
ortho–para-Directing Deactivators: Halogens
Halogens are ortho–para directors. They are more electronegative than carbon. Therefore, as ring substituents, they can withdraw electrons through ...
meta-Directing Deactivators: –NO2, –CN, –CHO, –CO2R, –COR, –CO2H
All meta-directing substituents are deactivating groups. These substituents withdraw electrons from the aromatic ring, making the ring less reactive ...
Directing and Steric Effects in Disubstituted Benzene Derivatives
When disubstituted benzenes undergo electrophilic substitution, the product distribution depends on the directing effect of both substituents. When the ...
Nucleophilic Aromatic Substitution: Addition–Elimination (SNAr)
Nucleophilic substitution in aromatic compounds is feasible in substrates bearing strong electron-withdrawing substituents positioned ortho or para to the ...
Nucleophilic Aromatic Substitution: Elimination–Addition
Simple aryl halides do not react with nucleophiles. However, nucleophilic aromatic substitutions can be forced under certain conditions, such as ...
Nucleophilic Aromatic Substitution of Aryldiazonium Salts: Aromatic SN1
Treating arylamines with nitrous acid gives aryldiazonium salts that are effective substrates in nucleophilic aromatic substitution reactions. The ...
Reduction of Benzene to Cyclohexane: Catalytic Hydrogenation
Unlike the easy catalytic hydrogenation of an alkene double bond, hydrogenation of a benzene double bond under similar reaction conditions does not take ...
Benzene to 1,4-Cyclohexadiene: Birch Reduction Mechanism
Birch reduction uses solvated electrons as reducing agents. The reaction converts benzene to 1,4-cyclohexadiene. The reaction proceeds by the transfer of ...
Hydrolysis of Chlorobenzene to Phenol: Dow Process
Simple aryl halides do not react with nucleophiles under normal conditions. However, the reaction can proceed under drastic conditions involving high ...
Benzene to Phenol via Cumene: Hock Process
The synthesis of phenol from benzene via cumene and cumene hydroperoxide is called the Hock process. First, a Friedel–Crafts alkylation reaction of ...
Oxidation of Phenols to Quinones
In the presence of oxidizing agents, phenols are oxidized to quinones. Quinones can be easily reduced back to phenols using mild reducing agents. The ...
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