Nitration and Resonance Structures

[Eiteiou]

Here is my assignment:

 

Drawresonance structures to show in which position nitrobenzene will nitrate toform dinitrobenzene.

 

I know that nitro groups are meta-directing, so the product will be m-dinitrobenzene. So do you just draw an intermediate carbocation with the charge in the meta position? If that's the case, where is the resonance? Would I show the charge being in the ortho, para, and meta positions but then indicate that the meta position is the most stable and therefore where substitution will occur??

 

Any advice is helpful, thank you!

 

 

[CarbonCopy]

If no2 substitutes in the ortho or para position, then the positive charge of the intermediate will resonate and a positive charge will be present on the other no2 of nitrobenzene. Since no2 is electron withdrawing, it withdraws from the positive charge making it even less stable. But, if no2 substitutes in the meta position, then no charge will be present on the other no2, in the resonance of intermediate. So, it does not destabilised positive charge. So, you should show resonance in the meta position where the charge does not resonate to the no2 group of nitrobenzene.

Edited November 16, 2012 by CarbonCopy