Sample 1Medium
Which order of stability of carbocations is correct?
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The answer is D.
Alkyl groups attached to the positive carbon stabilise it by hyperconjugation (and +I effect); the more C–H bonds alpha to the positive carbon, the more stable the cation. The tert-butyl cation (nine α-H) is most stable and CH3^+ (none) is least stable.
- A.
This is the reverse order; methyl cation has no hyperconjugation and is least stable.
- B.
The tertiary cation has more α-hydrogens than the secondary and is more stable, not less.
- C.
The methyl cation is the least stable, and more substituted cations are more stable, not less.
NCERT: Class 11 Chemistry, Chapter 8, 8.7