Problem: Select the TRUE statements below regarding Friedel-Crafts reactions.a) Friedel- Crafts reactions are sensitive to the presence of electron-withdrawing groups on the benzene ring. Friedel-Crafts reactions give poor yields when a strong or moderately deactivating substituent is present on the benzene ring. b) The use of a primary, secondary, or tertiary amine group on the benzene ring results in a better yield because the Lewis acid used in the Friedel-Crafts reaction reacts with the lone pair on the nitrogen atom to form an adduct and these substances are strong activators toward EAS reactions. c) Aryl and vinyl halides do not readily form carbocations and are not used in Friedel-Crafts reactions. d) Polyalkylations are worrisome in the Friedel-Crafts alkylation reaction. An alkyl group is an activator, and when one alkyl group has been placed onto a benzene ring, this activates the ring for further alkylations.e) Polysubstitutions are a problem in the Friedel-Crafts acylation reaction. The acyl group is a deactivator toward EAS and does not promote a further acylation of the benzene ring.

FREE Expert Solution

Select the TRUE statements below regarding Friedel-Crafts reactions.


Analyze each statement: 

a) Friedel- Crafts reactions are sensitive to the presence of electron-withdrawing groups on the benzene ring. Friedel-Crafts reactions give poor yields when a strong or moderately deactivating substituent is present on the benzene ring. 

  •  Friedel-Crafts reactions are usually preferred to be placed first in multistep synthesis due to this reason.
  • TRUE


b) The use of a primary, secondary, or tertiary amine group on the benzene ring results in a better yield because the Lewis acid used in the Friedel-Crafts reaction reacts with the lone pair on the nitrogen atom to form an adduct and these substances are strong activators toward EAS reactions. 

  • Aniline (NH2-benzene) derivatives ruin the Lewis Acid Catalyst
  • This means Friedel-Crafts reaction won't happen at all.
  • FALSE


c) Aryl and vinyl halides do not readily form carbocations and are not used in Friedel-Crafts reactions. 

  • This is a limitation for  Friedel-Crafts alkylation since the carbocation formed is very unstable. 
  • TRUE


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Problem Details

Select the TRUE statements below regarding Friedel-Crafts reactions.

a) Friedel- Crafts reactions are sensitive to the presence of electron-withdrawing groups on the benzene ring. Friedel-Crafts reactions give poor yields when a strong or moderately deactivating substituent is present on the benzene ring. 

b) The use of a primary, secondary, or tertiary amine group on the benzene ring results in a better yield because the Lewis acid used in the Friedel-Crafts reaction reacts with the lone pair on the nitrogen atom to form an adduct and these substances are strong activators toward EAS reactions. 

c) Aryl and vinyl halides do not readily form carbocations and are not used in Friedel-Crafts reactions. 

d) Polyalkylations are worrisome in the Friedel-Crafts alkylation reaction. An alkyl group is an activator, and when one alkyl group has been placed onto a benzene ring, this activates the ring for further alkylations.

e) Polysubstitutions are a problem in the Friedel-Crafts acylation reaction. The acyl group is a deactivator toward EAS and does not promote a further acylation of the benzene ring.

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