[daf44]

Hi,

I've been stuck at this problem for the last half hour, and I really don't know the answer.

It's about reaction A in the picture.

I would really appreciate if you all could help me.

[opsomath]

What do you know about each of these structures? Are they (respectively) nucleophiles or electrophiles?

[daf44]

I guess the left one is a electrophile and the right one a nucleophile (because of the negative charge on the oxygen)

[opsomath]

Yes. Actually the nitrogen on the right is more nucleophilic, since the oxygen anion is stabilized by resonance. So how can that nucleophile react with that electrophile? What is it about the nitrobenzene derivative on the left that makes it electrophilic?

[daf44]

So maybe the lone pair of the NH2 from the nucleophile attacks the benzene ring from the electrophile. It will attack the ring left to the F, because its a ortho/para director. Am I right?

[opsomath]

You're close. It will attack the carbon bonded to the F, and replace it. You are confusing electrophilic aromatic substitution (that's where the ortho para thing comes from) with nucleophilic aromatic substitution. Look up "nucleophilic aromatic substitution" on Wikipedia.

[daf44]

So the result shall be something like in the picture?

[opsomath]

That's right. Although, as a nitpick, COO- is plenty strong enough of a base to deprotonate HF. Probably this will be done in a basic environment in order to scavenge HF as it forms - do you have any more details on reaction conditions?

[daf44]

I don't have anymore information about the reaction conditions.

But I think this answer will do, thanks for the help   

[Sysiphus]

If you still want more information on this reaction, I suggest looking up Sanger reaction on wikipedia.

[Nosterius]

If you are interested to dwelve deeper in the subject, you could also take a look at "Meisenheimer complex"