Hydrocarbons - Result Question 44
####46. The restricted rotation about carbon carbon double bond in 2-butene is due to
[1993]
(a) Overlap of one $s$ - and $s p^{2}$ - hybridized orbitals
(b) Overlap of two $s p^{2}$ - hybridized orbitals
(c) Overlap of one $p$ - and one $s p^{2}$ - hybridized orbitals
(d) Sideways overlap of two $p$-orbitals.
Show Answer
Solution:
- (d) Restricted rotation about carbon carbon double bond in 2-butene is due to sideways overlap of two $p$-orbital.
Rotation around $\pi$ bond is not possible. If any attempt is made to rotate one of the carbon atoms, the lobes of $\pi$-orbital will no longer remain coplanar i.e no parallel overlap will be possible and thus $\pi$-bond will break . This is known as concept of restricted rotation. In other words the presence of $\pi$-bonds fix the position of two carbon atoms.
