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JEE Main · 2024 · 06 Apr 2024 · Shift 2 · General Organic Chemistry

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Number of carbocation from the following that are not stabilized by hyperconjugation is ______.
Structure A
A
Structure B
B
Structure C
C

Answer: 5

Solution

Hyperconjugation requires a (or ) bond on a carbon directly adjacent to the cationic centre. Cations such as the tert-butyl cation (three adjacent bonds) are hyperconjugatively stabilised; cations that instead sit next to a lone-pair-bearing atom (an ether oxygen or amine nitrogen) are stabilised by resonance rather than hyperconjugation, and cations with no adjacent C–H at all cannot be hyperconjugated. Working through the given set of structures, five of the cations lack an adjacent hyperconjugating C–H bond.
Structure A
A
Structure B
B
Structure C
C
Structure D
D

JEE Main · 2024 · 06 Apr 2024 · Shift 2 · Integer answer

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