[rleung]

Hey,

I have questions about the following two sets of illustrations.  In illustration A, I am wondering whether the second structure I have (with the ? near it) is a valid resonance form for the free radical structure on the left.  

For illustration B, my book lists both structures as resonance structures of the same free radical structure, I do not exactly understand why.  In the first structure to the left, there is only one lone electron on an oxygen, but in the second structure to the right, there are two lone electrons, one next to a respective oxygen.  How can these two be reonance structures?

Thanks.

Ryan

[rleung]

Illustration B

[movies]

B must be an error in your book.

[lemonoman]

'movies' is right.  That's Craaazzzyyy.  

P.S. A is definitely a valid resonance thing.  But, it may also be noteworthy that if you move one of oxygen's lone pairs, and form a double bond with the ring, you can play around with the ring's double bonds and find a couple more resonance structures.
 --> SIDE NOTE: Could another chemist clarify for both me and 'rleung'...We COULD make a resonance structure, doing as I said above.  This would throw off the nice resonance that benzene has in itself.  Would breaking up this first resonance be unfavorable?

[movies]

--> SIDE NOTE: Could another chemist clarify for both me and 'rleung'...We COULD make a resonance structure, doing as I said above.  This would throw off the nice resonance that benzene has in itself.  Would breaking up this first resonance be unfavorable?

Yes, disrupting the aromaticity of the benzene ring would be unfavorable, so those resonace structures would be higher in energy; they are still valid resonance structures, however.  The two drawn in the first post would be roughly equal in energy.  All the resonance structures contribute to the "actual" electronic structure, but of course the lower energy ones contribute more.