Aromatic Compounds and Electrophilic Substitution
Q. In the Friedel-Crafts alkylation of benzene, which of the following is a potential problem?
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A.
Polyalkylation
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B.
Dealkylation
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C.
Hydrogenation
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D.
Oxidation
Solution
Polyalkylation can occur in Friedel-Crafts alkylation, leading to multiple alkyl groups being added to the benzene ring.
Correct Answer: A — Polyalkylation
Q. What is the IUPAC name of the compound with the formula C6H5CH2OH?
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A.
Benzyl alcohol
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B.
Phenol
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C.
Benzene-1-ol
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D.
Benzeneethanol
Solution
The IUPAC name of C6H5CH2OH is benzyl alcohol, which consists of a benzene ring attached to a -CH2OH group.
Correct Answer: A — Benzyl alcohol
Q. What is the major product of the electrophilic substitution of benzene with bromine in the presence of FeBr3?
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A.
Bromobenzene
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B.
Benzyl bromide
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C.
Bromobenzyl
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D.
Benzene
Solution
The major product is bromobenzene, formed when bromine reacts with benzene in the presence of a Lewis acid catalyst like FeBr3.
Correct Answer: A — Bromobenzene
Q. What is the mechanism of the nitration of benzene?
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A.
Electrophilic addition
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B.
Nucleophilic substitution
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C.
Electrophilic substitution
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D.
Radical substitution
Solution
The mechanism of nitration of benzene is electrophilic substitution, where the nitronium ion acts as the electrophile.
Correct Answer: C — Electrophilic substitution
Q. What is the product of the electrophilic substitution of toluene with sulfuric acid?
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A.
Toluene sulfonic acid
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B.
Benzene sulfonic acid
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C.
Methyl sulfonic acid
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D.
Phenol
Solution
The product is toluene sulfonic acid, formed when toluene reacts with sulfuric acid in an electrophilic substitution reaction.
Correct Answer: A — Toluene sulfonic acid
Q. Which of the following compounds will undergo electrophilic aromatic substitution most readily?
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A.
Benzene
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B.
Toluene
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C.
Chlorobenzene
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D.
Nitrobenzene
Solution
Toluene will undergo electrophilic aromatic substitution most readily due to the electron-donating effect of the methyl group.
Correct Answer: B — Toluene
Q. Which of the following is a characteristic feature of electrophilic aromatic substitution reactions?
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A.
Formation of a carbocation
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B.
Formation of a sigma complex
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C.
Formation of a free radical
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D.
Formation of a carbanion
Solution
A characteristic feature of electrophilic aromatic substitution reactions is the formation of a sigma complex (arenium ion) during the reaction.
Correct Answer: B — Formation of a sigma complex
Q. Which of the following is a common electrophile used in the nitration of benzene?
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A.
Nitronium ion (NO2+)
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B.
Nitrate ion (NO3-)
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C.
Nitric acid (HNO3)
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D.
Ammonium ion (NH4+)
Solution
The nitronium ion (NO2+) is the active electrophile in the nitration of benzene, generated from nitric acid and sulfuric acid.
Correct Answer: A — Nitronium ion (NO2+)
Q. Which of the following substituents is a strong electron-donating group that activates the benzene ring towards electrophilic substitution?
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A.
Nitro group (-NO2)
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B.
Hydroxyl group (-OH)
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C.
Carboxylic acid (-COOH)
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D.
Halogens (-X)
Solution
The hydroxyl group (-OH) is a strong electron-donating group that activates the benzene ring towards electrophilic substitution.
Correct Answer: B — Hydroxyl group (-OH)
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