Aromatic Compounds and Electrophilic Substitution - Competitive Exam Level
Q. What is the effect of a methoxy group on the reactivity of a benzene ring in electrophilic substitution?
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A.
Deactivating and ortho/para directing
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B.
Deactivating and meta directing
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C.
Activating and ortho/para directing
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D.
Activating and meta directing
Solution
The methoxy group (-OCH3) is an activating group and directs electrophilic substitution to the ortho and para positions.
Correct Answer: C — Activating and ortho/para directing
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Q. What is the effect of a strong electron-withdrawing group on the reactivity of a benzene ring in electrophilic substitution?
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A.
Increases reactivity
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B.
Decreases reactivity
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C.
No effect
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D.
Reverses reactivity
Solution
A strong electron-withdrawing group decreases the reactivity of the benzene ring in electrophilic substitution by destabilizing the sigma complex.
Correct Answer: B — Decreases reactivity
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Q. What is the IUPAC name of the compound with the formula C6H5-CH2-COOH?
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A.
Benzyl acetic acid
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B.
Phenylacetic acid
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C.
Benzenepropanoic acid
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D.
Benzeneacetic acid
Solution
The correct IUPAC name is phenylacetic acid, as it has a phenyl group attached to the acetic acid structure.
Correct Answer: B — Phenylacetic acid
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Q. What is the IUPAC name of the compound with the formula C6H5CH2COOH?
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A.
Benzyl acetic acid
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B.
Phenylacetic acid
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C.
Benzenepropanoic acid
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D.
Benzeneacetic acid
Solution
The correct IUPAC name is phenylacetic acid, as it contains a phenyl group attached to an acetic acid moiety.
Correct Answer: B — Phenylacetic acid
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Q. What is the product of the reaction of benzene with sulfur trioxide (SO3) in the presence of sulfuric acid?
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A.
Benzene sulfonic acid
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B.
Benzene thiol
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C.
Benzene sulfide
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D.
Benzene sulfoxide
Solution
The product is benzene sulfonic acid, formed by the electrophilic substitution of sulfur trioxide on the benzene ring.
Correct Answer: A — Benzene sulfonic acid
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Q. What is the stereochemical outcome of the electrophilic substitution of toluene with chlorine?
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A.
Racemic mixture
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B.
Stereospecific
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C.
No stereochemistry
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D.
Enantiomers
Solution
Electrophilic substitution on toluene does not lead to stereochemistry as the reaction does not create a new stereocenter.
Correct Answer: C — No stereochemistry
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Q. What is the stereochemistry of the product formed when 1,2-dimethylbenzene undergoes electrophilic substitution?
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A.
Only one stereoisomer
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B.
Two stereoisomers
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C.
Three stereoisomers
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D.
No stereoisomers
Solution
Electrophilic substitution on 1,2-dimethylbenzene can lead to two different stereoisomers due to the presence of two methyl groups.
Correct Answer: B — Two stereoisomers
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Q. Which of the following compounds can undergo electrophilic substitution reactions?
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A.
Cyclohexane
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B.
Benzene
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C.
Hexane
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D.
Cyclopentane
Solution
Benzene can undergo electrophilic substitution reactions due to its stable aromatic system, while the other compounds cannot.
Correct Answer: B — Benzene
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Q. Which of the following compounds is most reactive towards electrophilic substitution?
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A.
Toluene
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B.
Benzene
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C.
Chlorobenzene
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D.
Nitrobenzene
Solution
Toluene is most reactive due to the electron-donating effect of the methyl group, which activates the ring towards electrophilic substitution.
Correct Answer: A — Toluene
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Q. Which substituent on a benzene ring is a deactivating group for electrophilic substitution?
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A.
Methyl
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B.
Methoxy
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C.
Nitro
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D.
Amino
Solution
The nitro group (-NO2) is a strong deactivating group due to its electron-withdrawing nature, making the ring less reactive towards electrophiles.
Correct Answer: C — Nitro
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