Chemistry · Alkyl and Aryl Halides
JEE Main 2024 — 9 April, Shift 1 — Question 67
Given below are two statements, one is labelled as Assertion (A) and the other is labelled asReason (R).
Assertion (A) : reaction of occurs more readily than the reaction of .
Reason (R) : The partially bonded unhybridised p-orbital that develops in the trigonal bipyramidal transition state is stabilised by conjugation with the phenyl ring.
In the light of the above statements, choose the most appropriate answer from the options given below :
- Option A:Correct
Both (A) and (R) are correct and (R) is the correct explanation of (A)
- Option B:
Both (A) and (R) are correct but (R) is not the correct explanation of (A)
- Option C:
(A) is correct but (R) is not correct
- Option D:
(A) is not correct but (R) is correct
Answer: A
Step-by-step solution
Assertion (A) is Correct: The reaction of benzyl bromide, , occurs more readily than the reaction of ethyl bromide, . This is because the reaction centre in benzyl bromide is the benzylic carbon, which is activated by the adjacent phenyl ring.
Reason (R) is Correct: In the transition state, a partially bonded, unhybridised -orbital character develops at the carbon undergoing nucleophilic attack. In benzyl bromide, this developing orbital is stabilised by conjugation with the phenyl ring through resonance.
The resonance stabilisation of the transition state lowers the activation energy, thereby increasing the rate of the reaction of benzyl bromide relative to ethyl bromide.
Thus, Both (A) and (R) are correct and (R) is the correct explanation of (A).
Answer key and solution verified before publishing.
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- Exam
- JEE Main 2024
- Paper
- 9 April, Shift 1
- Subject
- Chemistry
- Chapter
- Alkyl and Aryl Halides
- Topic
- Mechanism of Substitution reactions