Textbook Question
What products would you expect from the following coupling reactions?
(d)
(e)
19. Reactions of Aromatics: EAS and Beyond
Benzene Reactions
Multiple Choice
Which statement is incorrect regarding the reaction of with an ?
A
reacts with by nucleophilic aromatic substitution as the main mechanism.
B
The reaction typically requires a catalyst to activate the .
C
undergoes electrophilic aromatic substitution rather than addition reactions.
D
The aromaticity of is temporarily lost during the formation of the arenium ion intermediate.
Verified step by step guidance1
Recall that benzene typically reacts with electrophiles via electrophilic aromatic substitution (EAS), not nucleophilic aromatic substitution. This is because benzene's electron-rich π system attracts electrophiles, leading to substitution rather than addition or nucleophilic attack.
Understand that the reaction usually requires a Lewis acid catalyst (such as FeCl3 or AlCl3) to activate the electrophile, making it more electrophilic and able to attack the benzene ring.
Recognize that during the EAS mechanism, the aromaticity of benzene is temporarily lost when the electrophile forms a sigma complex (also called the arenium ion or sigma complex intermediate). This intermediate is resonance-stabilized but not aromatic.
Note that benzene does not typically undergo addition reactions with electrophiles because addition would disrupt the aromatic system permanently, which is energetically unfavorable.
Therefore, the incorrect statement is the one claiming that benzene reacts with electrophiles by nucleophilic aromatic substitution as the main mechanism, since the correct mechanism is electrophilic aromatic substitution.
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