[Altered State]

This is the last NMR I have to solve, but I'm in troubles again...

I do not definitely know what do that do that 2 separated proton integrals mean.



I thought of the structure I've drawn bellow, but still can't be the solution, because CH2 protons are coupling with methyl ones.

Facts:

The molecule has 2 insaturations. Don't know if that can mean double bond, carbonyl, or what else, in this case.
We have a CH3
I think we have a CH2
Don't what do the other 2 protons mean.


PS: This is my second post about NMR, and I'm new in this forum. I've read the rules, but I still don't know if I should open a new thread for every new question/problem I can't solve even if they are similar, or if I should post my doubts in the same thread as they are comming to my mind.

[discodermolide]

The other signals look like NH₂ or NH to me.
How would 5-aminopent-3-yn-2-one fit?

[Altered State]

I had to say that the formula is C4H7NO2

[discodermolide]

Thannks for telling us!

[Borek]

I've read the rules, but I still don't know if I should open a new thread for every new question/problem I can't solve even if they are similar, or if I should post my doubts in the same thread as they are comming to my mind.

Please open new threads for each problem.

[408]

that looks like two amine protons to me.

but with one nitrogen atom only, therefore they must be on the same nitrogen.  which means the c-NH2 bond can no longer freely rotate.  therefore we should be looking at amides.

H2NC(O)

we have a methyl and a CH2 coupling.  so an ethyl

that leaves a C, an O, and an unsaturation, so a CO again

now just stick them together and see what looks like it works.

I think I have the answer, but write your next try first

[Altered State]

we have a methyl and a CH2 coupling.  so an ethyl

I don't get this part.
My teacher gave us these exercises as no coupling ones.
And in the RMN we clearly don't see any coupling, so I definetly think that an ethyl cannot exist in this molecule.

Both of you said that the molecule will contain a NH2, and, as I understood, the 2 protons at ~6 and ~7 ppb are the ones bond with the nitrogen, isn't it? So why do they have diferent shifts?

I'm quite lost...

[Altered State]

I've read the rules, but I still don't know if I should open a new thread for every new question/problem I can't solve even if they are similar, or if I should post my doubts in the same thread as they are comming to my mind.

Please open new threads for each problem.

Thank you

[Altered State]

Thannks for telling us!

So it cannot be "pent-" like u said...

[discodermolide]

That is obvious.
It would be nice if you could supply all the info at the time of posting. The molecular formula, if you have it is important information.

[discodermolide]

I don't get this part.
My teacher gave us these exercises as no coupling ones.
And in the RMN we clearly don't see any coupling, so I definetly think that an ethyl cannot exist in this molecule.

Both of you said that the molecule will contain a NH2, and, as I understood, the 2 protons at ~6 and ~7 ppb are the ones bond with the nitrogen, isn't it? So why do they have diferent shifts?

I'm quite lost...
[/quote]

408 said the N is part of a H₂NC(O) system. Amides of such types often display two sets of signale due to the presence of rotamers.
look here at figure 11
http://www.chemistryexplained.com/Hy-Kr/Isomerism.html#b

[Altered State]

That is obvious.
It would be nice if you could supply all the info at the time of posting. The molecular formula, if you have it is important information.

Yes, my fault, I thought molecular formula was displayed on the picture I uploaded, but it seems to be not complete.





I think I finally got it! The main reason I possibly don't understeand you is becouse I'm currently learning English, is not my native language.

May it be something like this?

·······O
·······ll
H2N-C-CH2-C-CH3
·················ll
·················O

So we have 2 unsaturations that lead us to 2 C=O bonds, two protons bond with a nitrogen, one CH2 and one methyl with no coupling at all. And it fits with the molecular formula.
Isn't it?

[408]

because CH2 protons are coupling with methyl ones.

yes, the structure you posted is correct, I misread the above quote and thought the methyl and ethyl were coupling. 

[discodermolide]

Well done, on getting the structure.

[Altered State]

Btw, the structure seems correct, but ChemDraw gives me this NMR for it:



How would you explain that here amide protons appear in the same integral and in the model do not?