Benzylic Reactivity
Mediumchemistry
Benzylic bromides undergo SN1 faster than alkyl bromides due to:
Select the correct option:
Solution
Incorrect! Answer:
Resonance stabilization of benzylic carbocation
- Intermediate: In an SN1 reaction, the rate depends on how easily the metal-halogen bond breaks to form a carbocation.
- Benzylic System: In benzyl bromide (C6H5CH2Br), the resulting carbocation (C6H5CH2+) is adjacent to a benzene ring.
- Resonance: The positive charge on the methylene carbon is delocalized into the ortho and para positions of the aromatic ring through resonance.
- Stability: This resonance stabilization significantly lowers the activation energy for the first step, making benzylic halides exceptionally reactive in SN1 processes.
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About This Question
- Subject
- chemistry
- Chapter
- halogen organics
- Topic
- benzylic reactivity
- Difficulty
- Medium
- Year
- 2025
Solution
Correct Answer:
Resonance stabilization of benzylic carbocation
- Intermediate: In an SN1 reaction, the rate depends on how easily the metal-halogen bond breaks to form a carbocation.
- Benzylic System: In benzyl bromide (C6H5CH2Br), the resulting carbocation (C6H5CH2+) is adjacent to a benzene ring.
- Resonance: The positive charge on the methylene carbon is delocalized into the ortho and para positions of the aromatic ring through resonance.
- Stability: This resonance stabilization significantly lowers the activation energy for the first step, making benzylic halides exceptionally reactive in SN1 processes.
This medium difficulty chemistry question is from the chapter halogen organics, covering the topic of benzylic reactivity. It appeared in the 2025 exam.
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