elham90794
Registered: 09/26/09
Posts: 50
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Reply with quote | #1 |
I was wondering if someone could explain to me how they got 4 pi electrons in the p orbitals and not 5. Thank you! |
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mpadmabandu
Registered: 10/07/09
Posts: 5
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Reply with quote | #2 |
The 4 pi electrons come from the 2 double bonds in Ring C (2 e- each). This does not obey Huckel's rule, so the ring is not aromatic. The Thinkbook has some more examples of counting pi electrons on page 72, #5. |
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chemzilla09
Registered: 10/24/09
Posts: 7
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Reply with quote | #3 |
The 4 pi electrons come from the carbon nitrogen pi bond and the carbon to carbon pi bond. When counting pi electrons within a closed ring, you only count the electrons that are part of the closed ring. The double bond that connects the c ring to the rest of the molecule (which I assume is where you getting the 5th electron from) isn't directly part of the closed ring and thats why you don't count the electrons from it as part of the electrons in the closed ring. |
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am
Registered: 10/02/09
Posts: 19
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Reply with quote | #4 |
Wait, then how about the electrons from the lone pair on the nitrogen? How come that doesn't count? |
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chemzilla09
Registered: 10/24/09
Posts: 7
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Reply with quote | #5 |
The lone pair of electrons on the nitrogen does not contribute to the p orbital because it is part of the hybridized orbitals. Remember in this case the nitrogen atom is sp2, and since a p-orbital is already used to form the double bond with carbon, the lone pair has no choice but to occupy the one of the hybridized sp2 orbitals. |
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