JEE Advanced · 2013 · 02 Jun 2013 · Paper 1 · General Organic Chemistry

The hyperconjugative stabilities of tert-butyl cation and 2-butene, respectively, are due to

(A) $σ \to p$ (empty) and $σ \to π^{*}$ electron delocalisations.✓ Correct
(B) $σ \to σ^{*}$ and $σ \to π$ electron delocalisations.
(C) $σ \to p$ (filled) and $σ \to π$ electron delocalisations.
(D) $p$ (filled) $\to σ^{*}$ and $σ \to π^{*}$ electron delocalisations.

Answer: (A)

Solution

Tert-butyl cation: The positive charge creates an empty p-orbital. Hyperconjugation occurs through

σ \to p

(empty) electron delocalization from adjacent C-H bonds into the empty p-orbital.

2-butene: Hyperconjugation occurs through

σ \to π^{*}

electron delocalization from adjacent C-H bonds into the antibonding π* orbital of the C=C double bond.

Therefore, option (A) correctly describes both cases.

JEE Advanced · 2013 · 02 Jun 2013 · Paper 1 · One or more correct options

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JEE Advanced · 2013 · 02 Jun 2013 · Paper 1 · General Organic Chemistry

Solution

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