Ethene example


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Ashley McClearnen 1B
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Joined: Fri Sep 28, 2018 12:26 am

Ethene example

Postby Ashley McClearnen 1B » Mon Nov 26, 2018 6:08 pm

In the ethene example in lecture, why is there an unhybridized 2p orbital in addition to the hybridized 2sp2 orbital?

Fayez Kanj
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Joined: Fri Sep 28, 2018 12:18 am
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Re: Ethene example

Postby Fayez Kanj » Mon Nov 26, 2018 6:55 pm

Hello!

For Ethene, notice that each C has 3 regions of electron density. This means that the hybridization must be sp2 (by the conservation of orbitals law). Regular ethene has configuration 2s2, 2px1, 2px2. When it gets hybridized, an electron gets promoted from the 2s to the 2pz. The new configuration is 2s1, 2px1, 2py1, 2pz2. The hybridized state only needs 3 orbitals to form 3 sp2 hybridized orbitals, so it will use up the 2s, 2px, and 2py. The 2pz thus remains unhybridized.

Hope this helps :)

Jake Gordon 1A
Posts: 61
Joined: Fri Sep 28, 2018 12:15 am

Re: Ethene example

Postby Jake Gordon 1A » Mon Nov 26, 2018 11:07 pm

Any time you have a pi bond (double or triple bond) you will need one of the p orbitals to remain unhybridized. For carbon the configuration is 1s2 2s2 2p2 for 3 regions of electron density we will make an 2sp2 hybridization. This uses the s orbital and 2 p orbitals leaving one p orbital. 2s and 2p have 2 electrons each. These will fill the sp2 with one electron in each orbital and finally the last electron will fill the unhybridized p orbital. The sp2 orbitals will form sigma bonds and the final p orbital will make carbons p bond.

I hope this helps.


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