KVPY SA Exam 2018 Question Paper

Question : 74 of 80

Marks: +1, -0

The lower stability of ethyl anion compared to methyl anion and the higher stability of ethyl radical compared to methyl radical, respectively, are due to

+I effect of the methyl group in ethyl anion and σ → p-orbital conjugation in ethyl radical
–I effect of the methyl group in ethyl anion and σ → σ∗ conjugation in ethyl radical
+I effect of the methyl group in both cases
+I effect of the methyl group in ethyl anion and σ → σ∗ conjugation in ethyl radical

Validate

Solution:

CH_3 - C↖{-}H_2

is less stable than

C↖{-}H_3

as the

CH_3–

group exert +I effect

CH_3- C↖{ •}H_2

radical is more stablethan

C↖{ •}H_3

, this is due to σ-p conjugation, also known as hyperconjugation.

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