Double Pi Bonds


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Nicole Huang 3F
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Double Pi Bonds

Postby Nicole Huang 3F » Sat Dec 12, 2020 10:35 am

If there was a triple bond between two atoms between C and N, where both had a hybridization of 2sp, how would the bonding work? Is it a sigma bond formed between one sp orbital, and a pi bond with the other sp orbital; but then there would still need to be another pi bond because it's triple so I'm not sure which orbitals it would use to bond. I was wondering if anyone could explain how the bondings would work visually. Thanks!

For reference, it would like like:
[some molecule] - C ≡ N :
Last edited by Nicole Huang 3F on Sat Dec 12, 2020 10:44 am, edited 1 time in total.

505352202
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Re: Double Pi Bonds

Postby 505352202 » Sat Dec 12, 2020 10:42 am

The triple bond is composed of one σ bond and two π bonds. The sigma bond is formed from head-to-head overlap of the sp hybrid orbitals from the C and N atoms. The two π bonds in the triple bond are formed from overlap of the two unhybridized p atomic orbitals on each C and N atom.
Last edited by 505352202 on Sat Dec 12, 2020 10:47 am, edited 1 time in total.

Annie Tong 2G
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Re: Double Pi Bonds

Postby Annie Tong 2G » Sat Dec 12, 2020 10:46 am

I'm not entirely sure but here's my guess: carbon's hybridization would be 2sp ↑ ↑ and 2p ↑ ↑. Nitrogen is 2sp ↑ ↑ and 2p ↑↓ ↑ ↑. The 2sp overlap forms a sigma bond and the two 2p overlaps form two pi bonds. The ↑↓ in nitrogen's 2p orbital is its lone pair.

Silvi_Lybbert_3A
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Re: Double Pi Bonds

Postby Silvi_Lybbert_3A » Sat Dec 12, 2020 10:48 am

So with CN, there is a triple bond which means there will be one sigma bond and two pi bonds (this is always the case with a triple bond, at least for our purposes I believe). The C and the N both have 2sp hybridization as you said. But there are three p-orbitals (px, py, and pz), and only one of these p-orbitals is brought into hybridization with the 1s orbital. So, both carbon and nitrogen in this molecule have two unhybridized 2p orbitals each. These unhybridized orbitals are perpendicular to the hybridized orbital involved in the sigma bond (C2sp, N2sp). They are perpendicular to the hybridized orbital but also parallel to each other in the directions they point. They will bond with each other side-to-side (C2p, N2p). A really helpful way to figure this out and visualize it is using your fingers as Dr. Lavelle did in lecture.

This image shows triple bond (remember: each unhybridized p-orbital has two lobes).
Attachments
Screen Shot 2020-12-12 at 10.49.14 AM.png

Chenning Yang Dis3l
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Re: Double Pi Bonds

Postby Chenning Yang Dis3l » Tue Dec 15, 2020 10:33 am

This is a great question! I was wondering.

kristinalaudis3e
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Re: Double Pi Bonds

Postby kristinalaudis3e » Tue Dec 15, 2020 8:10 pm

So in a triple bond, one is a sigma bond and 2 are pi bonds. For the sigma bonds, they will overlap end to end, but for the pi bonds, they have to overlap side by side. The 2 pi bonds are formed when the unoccupied p orbitals that are not overlapping end to end then overlap side by side with the other unoccupied p orbitals.

Jaclyn Schwartz 1I
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Re: Double Pi Bonds

Postby Jaclyn Schwartz 1I » Wed Dec 16, 2020 10:50 am

In a triple bond, there is one sigma bond and two pi bonds. I believe sigma bonds are end to end while pi bonds are side to side bonds.


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