May 17, 2022, 10:34:42 AM
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### Topic: Orbital Coefficients for CO  (Read 454 times)

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#### Jacobthebus

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##### Orbital Coefficients for CO
« on: February 28, 2021, 10:53:04 AM »
Hi all!

I'm working through MO theory concerning diatomic molecules and I've attempted to draw out a MO diagram for CO. I'm aware that CO exhibits sp mixing, and this skews the energy of certain bonding orbitals. This issue I'm having is working out the shapes of the bonding/antibonding orbitals, and why some orbital lobes are greater in magnitude towards Oxygen, and others towards Carbon.

I understand that the size of orbital lobes depends on how close the MOs are to the AOs in terms of energy, but sp mixing is making this difficult to understand.

I've attached added a link to the relevant MO diagram, along with the orbitals.

https://www.researchgate.net/profile/Carlos-Romao/publication/221846847/figure/fig3/AS:393964566925314@1470939880217/left-Simplified-MO-diagram-of-CO-with-electronic-occupancy-in-the-ground-state-The.png

Best wishes,
Jacob

#### Orcio_87

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##### Re: Orbital Coefficients for CO
« Reply #1 on: March 07, 2021, 10:00:52 AM »

If you take hybridization into account then:

Carbon atom has configuration: 1s2, 2sp1, 2sp1, 2py1, 2pz1

While oxygen atom has: 1s2, 2s2, 2sp2, 2sp2, 2py1 2pz1.

But carbon 1s2 and oxygen 1s2 atomic orbitals don't form any molecular orbitals.

Carbon and oxygen 2py 2pz are overlaping and form two π orbitals (bonding orbitals).

Four sp hybrids overlaps and gives four molecular orbitals - sσ, pσ, sσ* and sσ*, but the last one is empty due to lack of electrons.

Four of six electrons on this orbitals comes from oxygen, so one bond is coordination bond from oxygen to carbon, and bond order equals 3, similiar to N2.
« Last Edit: March 07, 2021, 01:39:14 PM by Orcio_Dojek »

#### Orcio_87

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##### Re: Orbital Coefficients for CO
« Reply #2 on: March 07, 2021, 01:35:51 PM »
@Jacobthebus

Quote
why some orbital lobes are greater in magnitude towards Oxygen, and others towards Carbon

General rule is that bonding orbitals are more concentrated on more electronegative element.

That is why orbital sσ and pσ are located rather on oxygen than carbon atom, and orbital sσ* is located on a carbon atom.

- - - - - - - - - - -

Also (in my opinion) - hybridization is not 100 % complete, that is why there are four different (sσ, pσ and sσ*, pσ*) MO, and not two sets (two sp σ and two sp σ*) molecular orbitals.
« Last Edit: March 07, 2021, 02:21:49 PM by Orcio_Dojek »