Sigma and Pi Bonds [ENDORSED]

$sp, sp^{2}, sp^{3}, dsp^{3}, d^{2}sp^{3}$

Jacqueline Duong 1H
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Joined: Fri Sep 28, 2018 12:28 am

Sigma and Pi Bonds

Can someone please explain sigma and pi bonds and how they are formed?

Chem_Mod
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Re: Sigma and Pi Bonds

Sigma and Pi bonds are formed by the overlap of atomic orbitals. Sigma bonds are formed by end-to-end overlapping and Pi bonds are when the lobe of one atomic orbital overlaps another. These orbitals are the same orbitals that we talked about in previous lectures (s, p, d, etc.).

Nick Bazett 1F
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Re: Sigma and Pi Bonds

What are the shapes of Sigma and Pi bonds?

Jessica Chen 1F
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Re: Sigma and Pi Bonds  [ENDORSED]

Something to add on is that all single bonds are sigma bonds, all double bonds have one sigma and one pi bond, and all triple bonds have one sigma and two pi bonds and so on (all have one sigma, the rest are pi bonds). The sigma bonds allow the molecule to rotate, but the pi bonds are rigid and lock the molecule into place so that it is unable to rotate.

Rithana Srikanth 3L
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Re: Sigma and Pi Bonds

The shapes of sigma bonds are more spherical, whereas pi bonds look like a dumbbell with the lobes on either end of the bond axis.

mayra martinez 1D
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Re: Sigma and Pi Bonds

Adding on to that, sigma bonds are more spherical because they correspond with the s-orbital. The pi bonds are more dumbell shape and they correspond with the p-obitals.

Louis Zhao 4C
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Re: Sigma and Pi Bonds

Does anyone know the reason why pi bonds cannot rotate while sigma bonds can, so like how does the structure of each bond result in their ability to rotate?

Megan_Ervin_1F
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Re: Sigma and Pi Bonds

Why was doctor Lavelle talking about how sigma and pi bonds rotate and some cannot rotate because they snap? Could someone explain?

Laura Gong 3H
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Re: Sigma and Pi Bonds

Sigma bonds have their electron density along the bond axis and cylindrical in shape which allow for rotation. Pi bonds have their electron density above and below the bond axis. Their orbitals overlap side by side which makes them rigid, trying to rotate that bond would result in breaking that bond.

Meigan Wu 2E
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Re: Sigma and Pi Bonds

Also, sigma bonds are made from hybridized orbitals and pi bonds are made from unhybridized orbitals.

Angela Cong 3C
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Re: Sigma and Pi Bonds

pi bonds are bonded side by side different than sigma bonds, because of the physical structure, rotating the molecule along the sigma bond would cause the pi bond to snap.

Bianca Barcelo 4I
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Re: Sigma and Pi Bonds

Meigan Wu 3I wrote:Also, sigma bonds are made from hybridized orbitals and pi bonds are made from unhybridized orbitals.

What happens when a d orbital is involved in hybridization? Does that affect the shape in any way?

Saachi_Kotia_4E
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Joined: Fri Sep 28, 2018 12:23 am

Re: Sigma and Pi Bonds

sigma bonds involve a single overlap, such as when two s orbitals overlap, or one s overlaps with a p orbital. pi bonds involve a double overlap, such as when two p orbitals overlap side by side, so that they are inflexible. this is why pi bonds are stronger