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

1. σ → p (empty) and σ → π⁺ electron delocalisations
2. σ → σ⁺ and σ → π electron delocalisations
3. σ → p (filled) and σ → π electron delocalisations
4. p (filled) → σ → π⁺ electron delocalisations

Correct answer: σ → p (empty) and σ → π⁺ electron delocalisations

Solution

The stability of the tert-butyl cation arises from σ → p (empty orbital) delocalization, while the stability of 2-butene is due to σ → π⁺ delocalization, both of which involve electron donation to stabilize the system.

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