Discussion Forum



1)

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


A) $\sigma\rightarrow p$ (empty) and $\sigma\rightarrow \pi^{*}$ electron delocalisations

B) $\sigma\rightarrow \sigma^{*}$ and $\sigma\rightarrow \pi$ electron delocalisations

C) $\sigma\rightarrow p$ (filled) and $\sigma\rightarrow \pi^{}$ electron delocalisations

D) $p(filled)\rightarrow \sigma^{*}$ and $\sigma\rightarrow \pi^{*}$ electrons delocalisations

Answer:

Option A

Explanation:

Plan spreading out charge by the overlap of an empty p-orbital with an adjacent $\sigma$ bond is called hyperconjugation. This overlap(the hyperconjugation)  delocalised the positive charge on the carbocation, spreading it over a larger volume, and this stabilises the carbocation.

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tertiary butyl carbocation has one vacant p-orbital hence, it is stabilised by $\sigma$ -p  (empty) hyperconjugation.

1042021418_c9.JPG

   In 2-butene stabilisation is due to hyperconjugation  between $\sigma$ -$\pi^{*}$  electron delocalisations