Due to the decrease in electron density on the nitrogen atom, this salt deactivates the benzene ring towards further reaction. As a result, aniline does not undergo the Friedel-Crafts reaction.
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Questions
Give reasons for the following:
Aniline does not undergo Friedel- Crafts reaction.
Account for the following:
Aniline does not undergo Friedel-Crafts reaction.
Why aniline does not undergo Friedel-Crafts reaction?
Chemical Equations/Structures
Give Reasons
Short Answer
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Solution 1
A Friedel-Crafts reaction is carried out in the presence of AlCl3. But AlCl3 is acidic in nature, while aniline is a strong base. Thus, aniline reacts with AlCl3 to form a salt (as shown in the following equation).
Due to the positive charge on the N-atom, electrophilic substitution in the benzene ring is deactivated. Hence, aniline does not undergo the Friedel-Crafts reaction.
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Solution 2
The Friedel-Crafts reaction is an electrophilic substitution reaction that occurs in the presence of aluminium chloride (AlCl3) as a catalyst. AlCl3 acts as a Lewis acid, while aniline is a base. Therefore, their reaction forms a salt:
\[\ce{C6H5NH2 + AlCl3 -> \underset{(Salt)}{C6H5NH^+_2AlCl^-_3}}\]
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Chapter 9: Amines - Exercises [Page 278]
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