Why are #pi# orbitals doubly-degenerate?

1 Answer
Truong-Son N.
Oct 15, 2017

Because they formed from the equivalent sidelong interactions of #p_x# and #p_y# orbitals, which, aside from their entire orientations, are the same orbitals. As a result, all #pi# interactions are doubly-degenerate.

There is no difference, in principle, between the #p_x-p_x# atomic orbital overlap and the #p_y-p_y# atomic orbital overlap other than their relative entire orientations.

http://butane.chem.uiuc.edu/

In fact, if you envision using your right hand to take the #pi_(2px)# molecular orbital and rotate it #90^@# counterclockwise about the #z# axis, you get exactly the #pi_(2py)# molecular orbital.

So, they are the same energy molecular orbitals.

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