[SSThree]

Ok so Im working away at my assignment, and Im stuck on this one question.  It describes my molecule as one that was originally used to treat headaches that is extracted from the bark of a tree.
Im thinking great, its Salicylic Acid or some other derivative form the willow tree.  Problem is the molecular weight is 138 and the molecule listed in the question has a MW of 121.
Anyways, heres what we know:
MW=121
Aromatic, comes from the bark of a tree
2 doublets and a singlet in the aromatic region of NMR
Broad singlet at 4ppm
Sharp singlets at 1.5 and 1.6ppm

Also, the is no reaction between HCl and BR2
But when NaNO2 and HCl are reacted, after H3PO2 is added the entire NMR had only 4 peaks

From what I know so far, H3PO2 will change a Diazonium branch on the benzene to a hydrogen, and release N2 gas
NaNO2 and HCl will make a NH2 branch into a Diazonium ion.
The only reason I could think to use the Diazonium is to have 3 substituants in the meta positions to eachother, but this wouldnt give us doublets in the NMR spec.

Thanks in advance guys/gals

[macman104]

Do you have integrations on your NMR?  Broad singlet at 4ppm, sounds like some sort of OH group.

[SSThree]

The Broad singlet at 4ppm integrates for 2H and the singlets at 1.5 and 1.6ppm integrate for 3H each.

I actually read the question wrong, when the molecule is reacted with Br2 (excess), the aromatic region only has 2 signals, THEN when its reacted with HCl and Br2 there is no reaction.

Gunna do up a quick drawing in chemdraw

[SSThree]

So when the Br2 is added in excess, the ortho position to the left of the NH2 will have a Br because NH2 is a strong activator. When more Br2 is added, no reaction occurs which means X and Y are Strong deactivators/ Meta directors.

[SSThree]

Also, given the reaction with the Diazonium, we would have a product that has a plane of symetry down following line:


Therefore X and Y are actually the same, and both only have one signal in the NMR (like a OH or CH3)

Sorry for post-whoring, just thinking out loud

[azmanam]

I think you're on the right track.  The molecule I'm thinking of matches the mass, and sorta matches the NMR (although the upfield shifts for the compound I'm thinking of come 2.0 and 2.1).  Keep on your line of thinking, I think you'll get there.

[SSThree]

Ok Think O solved it.

Heres the final structure:


My reasoning is that in our reaction with Br2 will yield a product with a Br in the ortho position to the NH2, since thats where all the substituants direct to.  That is the only available position for Br2 therefore on amount of catalyst or Br2 will add another Br2 to the ring, since NH+ are meta directors and strongly deactivating.

In our reaction with the diazonium, the NH2 is replaced with a H and there are only 4 signals due to the mirror plane.

Thoughts?

Am I right?

[macman104]

I think I'm going to call your answer creative .  However, I don't think that compound is likely to exist (the nitrogens are not at full valency, and I doubt they exist).  Also, that does not give you your sharp singlets of 3H.  The NH2 seems reasonable given your facts however.

[SSThree]

Hmm what if the NH+ were replaced with a methyl group, that would give a sharp singlet of 3H no?

Both NH+ and CH3 have a MW of about 15.

[macman104]

Correct, those would give two singlets, and they are also in different environments, so they have slightly different shifts.  Now step back through the steps of the reaction and characterizations and see if they make sense together.

[SSThree]

Cool! Makes sense.

Thanks guys