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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: ramboacid on March 04, 2014, 11:26:25 PM

Title: Polyatomic MO Diagrams for Localized vs Delocalized pi bonds
Post by: ramboacid on March 04, 2014, 11:26:25 PM

A question from chapter 6 of Oxtoby's General Chemistry:

"Formulate the MO structure of (NO₂⁺) for localized pi bonds and delocalized pi bonds. Is it linear or nonlinear? Do you expect it to be paramagnetic? Repeat the analysis for NO₂ and NO₂^-."

I understand how to determine the geometry and paramagnetism/diamagnetism of a molecule given its electronic structure. However, I don't understand how to depict an MO diagram with delocalized pi bonds - all the diagrams I've seen so far have been for diatomic molecules, and the internet (so far) has been relatively unhelpful with polyatomic MO diagrams.

How does one go about drawing MO diagrams for a molecule that can show or not show delocalized pi bonds for that molecule?

Title: Re: Polyatomic MO Diagrams for Localized vs Delocalized pi bonds
Post by: Corribus on March 05, 2014, 11:25:36 AM

Hard to show how to draw MO diagrams without being right next to you with a piece of paper and a pen. But for small polyatomics, the best way is to use SALCs and LGOs, which requires an understanding of group theory. Walsh diagrams are a handy way to determine bent/linear. Are you familiar with these concepts?

If so, maybe you find this useful:

http://www.lasalle.edu/~prushan/IC-articles/Polyatomic%20Molecular%20Orbital%20Theory.pdf

I admit to being a little confused by the distinction between localized and delocalized pi bonds in this case.