How does singlet oxygen work in pericyclics?

AI Thread Summary
The discussion focuses on the electronic structure of the 1E+g dienophile, particularly the nature of its LUMO and the implications of having two LUMOs. The presence of unpaired electrons in degenerate pi orbitals raises questions about reactivity, suggesting that this could enhance the compound's instability and reactivity due to the presence of diradical characteristics. The participant critiques the MO diagram for singlet oxygen found on Wikipedia, arguing that it inaccurately represents the orbital occupancy, specifically pointing out that the correct representation involves a combination of pi orbitals. The conclusion drawn is that if one of the pi* orbitals is doubly occupied, the other serves as the LUMO, which is significant for understanding the compound's reactivity.
CrimpJiggler
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0dd50c496df40e817213b79f87298753.png

and here's the diagram for the 1O2 dienophile:
1efc1d4587d91c99eaf8224ed3667f8d.png

Its the 1E+g the one I'm interested in. I see that its single electrons are in a couple of degenerate pi orbitals. I'm having trouble figuring out what the LUMO is here. Does it even matter that I have 2 LUMOs? I kinda suspect, that would make it much more reactive since unpaired electrons are pretty unstable. Is this oxygen singlet species technically a diradical?
 
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The MO diagram for singlet oxygen from wikipedia is not quite correct insofar as it is not a pi_x or pi_y orbital which is doubly occupied in singlet oxygen but rather a ##\pi^*_\pm=\frac{1}{\sqrt{2}}(\pi^*_x\pm i\pi^*_y)## orbital.
So let's say that the ##\pi^*_+## is doubly occupied, then the ##\pi^*_-## is the LUMO.
 

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