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Aromatic Substrate Requirements
MCQ questions and answers.
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MCQ Questions
1. Which aromatic compound is most suitable as the substrate for Friedel–Crafts acylation?
A.
Benzene
B.
Nitrobenzene
C.
Benzenesulfonic acid
D.
Trifluoromethylbenzene
Correct Answer:
Benzene
Explanation:
Benzene is an electron-rich aromatic ring with available hydrogen atoms, so it readily undergoes Friedel–Crafts acylation.
2. Why is nitrobenzene generally unsuitable for Friedel–Crafts acylation?
A.
The nitro group strongly activates the ring
B.
The nitro group strongly deactivates the ring
C.
Nitrobenzene has no aromatic ring
D.
Nitrobenzene contains too many hydrogen atoms
Correct Answer:
The nitro group strongly deactivates the ring
Explanation:
The nitro group withdraws electron density from the benzene ring, making the ring too unreactive toward Friedel–Crafts acylation.
3. Which feature is generally required in an aromatic substrate for Friedel–Crafts acylation?
A.
An electron-rich aromatic ring
B.
A saturated carbon chain only
C.
A strongly electron-deficient ring
D.
A ring with no hydrogen atoms
Correct Answer:
An electron-rich aromatic ring
Explanation:
Friedel–Crafts acylation occurs more readily when the aromatic ring has sufficient electron density to attack the acylium ion.
4. Which compound is suitable for Friedel–Crafts acylation because its methyl group activates the benzene ring?
A.
Toluene
B.
Nitrobenzene
C.
Benzenesulfonic acid
D.
Chlorobenzene
Correct Answer:
Toluene
Explanation:
The methyl group releases electron density toward the ring, making toluene more reactive toward Friedel–Crafts acylation than benzene.
5. Aromatic substrates used in Friedel–Crafts acylation should usually contain which type of ring?
A.
An activated or sufficiently reactive benzene ring
B.
A strongly deactivated benzene ring
C.
A nonaromatic cyclohexane ring
D.
A ring containing only heteroatoms
Correct Answer:
An activated or sufficiently reactive benzene ring
Explanation:
The aromatic ring must be reactive enough to undergo electrophilic substitution with the acylium ion.
6. Which substituent makes an aromatic ring less suitable for Friedel–Crafts acylation?
A.
Methyl group
B.
Ethyl group
C.
Nitro group
D.
Isopropyl group
Correct Answer:
Nitro group
Explanation:
A nitro group strongly withdraws electron density and deactivates the aromatic ring, preventing or greatly hindering Friedel–Crafts acylation.
7. Why can strongly deactivated aromatic rings fail to undergo Friedel–Crafts acylation?
A.
They cannot form an aromatic ring
B.
They are not electron-rich enough to attack the electrophile
C.
They contain too many carbon atoms
D.
They always react only by addition
Correct Answer:
They are not electron-rich enough to attack the electrophile
Explanation:
The aromatic ring must provide electron density for electrophilic substitution; strongly deactivated rings cannot do this effectively.
8. Which aromatic compound is generally unsuitable for Friedel–Crafts acylation because of strong ring deactivation?
A.
Ethylbenzene
B.
Toluene
C.
Nitrobenzene
D.
Benzene
Correct Answer:
Nitrobenzene
Explanation:
Nitrobenzene is strongly deactivated by the nitro group, so it generally does not undergo Friedel–Crafts acylation.
9. For Friedel–Crafts acylation, the aromatic substrate normally undergoes which type of reaction at an available ring hydrogen?
Explanation:
The acyl group replaces a hydrogen on a sufficiently reactive aromatic ring through electrophilic aromatic substitution.
10. Which statement about benzene as an aromatic substrate in Friedel–Crafts acylation is correct?
A.
Benzene is too strongly deactivated to react
B.
Benzene has available ring hydrogens and can undergo acylation
C.
Benzene is not an aromatic compound
D.
Benzene can react only if its ring hydrogens are removed first
Correct Answer:
Benzene has available ring hydrogens and can undergo acylation
Explanation:
Benzene is a suitable aromatic substrate because it has an electron-rich aromatic ring with hydrogen atoms that can be replaced by an acyl group.
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