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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: daf44 on August 05, 2011, 12:19:35 PM

Title: Organic chemistry reaction problem
Post by: daf44 on August 05, 2011, 12:19:35 PM

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.

(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fi53.tinypic.com%2Fim3335.jpg&hash=c68716b818b4853bb06851f1b91313f77abe5152)

Title: Re: Organic chemistry reaction problem
Post by: opsomath on August 05, 2011, 12:31:10 PM

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

Title: Re: Organic chemistry reaction problem
Post by: daf44 on August 05, 2011, 01:09:53 PM

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

Title: Re: Organic chemistry reaction problem
Post by: opsomath on August 05, 2011, 01:14:20 PM

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?

Title: Re: Organic chemistry reaction problem
Post by: daf44 on August 05, 2011, 01:25:02 PM

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?

Title: Re: Organic chemistry reaction problem
Post by: opsomath on August 05, 2011, 02:04:43 PM

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.

Title: Re: Organic chemistry reaction problem
Post by: daf44 on August 05, 2011, 06:57:47 PM

So the result shall be something like in the picture?

(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fi53.tinypic.com%2F2v9w8dc.jpg&hash=440b282e4e2d35a81efac1a7538791da61d04b33)

Title: Re: Organic chemistry reaction problem
Post by: opsomath on August 05, 2011, 08:30:41 PM

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?

Title: Re: Organic chemistry reaction problem
Post by: daf44 on August 06, 2011, 07:07:41 AM

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

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

Title: Re: Organic chemistry reaction problem
Post by: Sysiphus on August 07, 2011, 07:57:51 PM

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

Title: Re: Organic chemistry reaction problem
Post by: Nosterius on August 10, 2011, 09:47:34 AM

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