Organic Chemistry Basics Result Question 52
The hyperconjugative stabilities of tert-butyl cation and 2-butene, respectively, are due to
(2013 Adv.)
(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
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Answer:
Correct Answer: 52. ( a )
Solution:
Spreading out charge by the overlap of an empty $p$-orbital with an adjacent $\sigma$-bond is called hyperconjugation. This overlap (the hyperconjugation) delocalises the positive charge on the carbocation, spreading it over a larger volume, and this stabilises the carbocation.
tertiary butyl carbocation has one vacant $p$-orbital, hence, it is stabilised by $\sigma-p$ (empty) hyperconjugation.
BETA
