Pi Bonds  [ENDORSED]

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Yasmin Olvera 1D
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Joined: Thu Feb 14, 2019 12:15 am

Pi Bonds

Postby Yasmin Olvera 1D » Tue Jul 30, 2019 12:52 pm

Why do Pi bonds not allow free rotation? Is this always the case?

Chem_Mod
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Re: Pi Bonds

Postby Chem_Mod » Tue Jul 30, 2019 1:13 pm

Yes, always the case.
As I showed in class for the p-orbitals to overlap (in phase) they need to be in the same plane (side-by-side) to form a pi-bond. If the atoms rotate then p-orbitals are not in the same plane and therefore are not overlapping.

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Chem_Mod
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Re: Pi Bonds  [ENDORSED]

Postby Chem_Mod » Tue Jul 30, 2019 1:16 pm

Pi bonds are formed by the overlap of two unhybridized p orbitals. There will be a bond above and below the sigma bond. This pi bond is only stable in one orientation so there cannot be any free rotation. There can never be free rotation around a bond formed by parallel overlap. This is why pi bonds are weaker than sigma bonds and why you cannot rotate around a double bond.

Gwynneth Orlino 1B
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Re: Pi Bonds

Postby Gwynneth Orlino 1B » Tue Jul 30, 2019 1:22 pm

Pi bonds don't allow rotation because the two parallel atomic orbitals have two areas of overlap. So if one of the atoms were to rotate, the orbitals would no longer overlap and the pi bond would break.


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