The hyperconjugative stabilities of tert-butyl cation and 2-butene, re

1.	The hyperconjugative stabilities of tert-butyl cation and 2-butene, respectively, are due to
Answer» `SIGMA-p` (empty) and `sigma-pi^()` electron delocalisations `sigma-sigma^()` and `sigma-pi^()` electron delocalisations `sigma-p` (filled) and `sigma-pi` electron delocalisations p (filled) `rarr sigma^()` and `sigma-pi^()` electron delocalisations Solution :In tert-butyl CATION, the CARBON bearing positive charge has an empty p-orbital and hence hyperconjugation here INVOLVES `sigma`-p (empty) electron delocalisation. In 2-butene, `pi`-bond contains two electrons, one electron from each of the two carbon atoms, i.e., `pi`-MO contains a PAIR of electrons, but `pi^()` MO is empty and hence electrons of the `sigma` C-H bond can move only into the `pi^(**)` orbital. Thus, option (a) is correct.

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