Resonance structure

[aurorab]

Hello everybody. Could you help me with the resonance structure of p-nitro - methylobenzene? I would appreciate it.

Is any of them correct?

[Elite Engineer]

They look correct to me.

[hypervalent_iodine]

In fact, neither image is correct at all.

 

Firstly, you are missing the + charge on the nitrogen in all of them. A nitrogen with 4 bonds will have a + charge. If it didn't, the nitrobenzene would have a - charge, but it doesn't.

 

You first image looks very bizarre. Why have you got all three double bonds breaking in the ring like that? Even if that did happen (it definitely doesn't), you've completely missed out the 3 positive charges that would be on the other carbons in the ring.

 

The second one is also a bit off. In the first step, why do you take the electrons away from the oxygen rather than the double bond in the ring? What you have drawn, which generates a + charge on the oxygen, doesn't make a lot of chemical sense. This will change the charge you have put on the ring. Even if your first step were correct, you would still be missing a structure between your last resonance structure and the original one.

[aurorab]

Thank you very much!

"In the first step, why do you take the electrons away from the oxygen rather than the double bond in the ring?"

Because of R+.

Edited January 21, 2016 by aurorab

[hypervalent_iodine]

Thank you very much!

No problems.

 

"In the first step, why do you take the electrons away from the oxygen rather than the double bond in the ring?"

Because of R+.

I don't know what you mean by this. In any case, it's wrong. The electrons don't move that way. You generate a positive charge in the ring, not a negative one.

 

Could you explain your logic behind the first image? I'm struggling to understand what you were trying to do there.