Question

The hyperconjugative stabilities of tert-butyl cation and `2`-butene, respectively, are due to
A. `sigma rarr p` (empty) and `sigma rarr pi^(**)` electron delocalisations
B. `sigma rarr sigma^(**)` and `sigma - rarr` electron delocalisations
C. `sigma rarr p` (filled) and `sigma rarr pi` electron delocalisations
D. p (filled) `rarr sigma^(**)` and `sigma rarr pi^(**)` electron delocalisations

Answer 1

Correct Answer - A
`{:(" "H,," "H^(o+)),(" |",,),(" "CH_(2),," "CH_(2)),(" |",," ||"),(CH_(3)-C^(o+),,CH_(3)-C),(" |",," |"),(" "CH_(3),," "CH_(3)):}`
In tert-butyl cation, bearing `o+` charge has one vacant p orbital hence it is `sigma`- p (empty) conjugation or Hyperconjugation.

In 2-butene hyperconjugation between `sigma` and `pi^(**)` bond.