[hellen]

      Hello, everyone! I am a green hand and wish your *delete me* thanks!

       the compound is white solid, melting point:130--132?,dissolve in alcohol and water,don`t dissolve in chloroform.  In addition C13 NMR show the C of -CO-, the C of -CH2- and the C of the -CH3, but haven`t the C13 NMR ( the result is told by my coworker)

     As so far, I known these. Please help me, thank you very much!

[hellen]

sorry,I forgot  I have the HPLC and UV of the compound too!

PLEASE *delete me* THANKS!!

[kiwi]

hard to make a call without details of the synthesis, but here goes.

1)product is clearly polar (solubility)
2)contains an ethyl group (1H NMR)
3)contains a carboxy group (IR, NMR)

from the IR looks like you have NH stretches up around 3300cm-1. It can't be propionamide (mp ~80 degC, and the br s is all wrong for an amide). with the limited information available, maybe ammonium propionate? but this doesn't fit all the data (MS), so any further info would help

[Sam (NG)]

hard to make a call without details of the synthesis, but here goes.

1)product is clearly polar (solubility)
2)contains an ethyl group (1H NMR)
3)contains a carboxy group (IR, NMR)

from the IR looks like you have NH stretches up around 3300cm-1. It can't be propionamide (mp ~80 degC, and the br s is all wrong for an amide). with the limited information available, maybe ammonium propionate? but this doesn't fit all the data (MS), so any further info would help

according to my spectroscopy textbook, the chemical shift for an amide proton can be anywhere between 5 and 12 ppm, and a search on the net revealed N-H protons at 5.6, can you please explain why this is not correct?

[english]

It may help if you follow the spectral analysis in this order:

MS ---> IR ---> H NMR

Remember that the highest m/z value is usually your molecular mass (molecular fragments, along with their abundance, are usually just used to validate the compound; you can generally ignore these for the overall determination in a problem like this).  Then use IR to determine what functional groups are present.  With that information, you can deduce the mass due to carbon and hydrogen only.  You should now have a decent molecular formula.

Now use your H NMR to get the structure.

[Sam (NG)]

It may help if you follow the spectral analysis in this order:

MS ---> IR ---> H NMR

Remember that the highest m/z value is usually your molecular mass (molecular fragments, along with their abundance, are usually just used to validate the compound; you can generally ignore these for the overall determination in a problem like this).  Then use IR to determine what functional groups are present.  With that information, you can deduce the mass due to carbon and hydrogen only.  You should now have a decent molecular formula.

Now use your H NMR to get the structure.

Surely there could be multiply charged ions due to the fact that it was Electrospray Ionisation?  If so, the m/z could only be a fraction of the real Molecular Mass.  (Not that i'm saying that this is the case here, it doesn't look like it to me, i'm still a little bemused as to how you get a mass of 360 and only 3 ¹H environments.)

[hellen]

 :)THANKS EVERYONE!

     I prefer to the molcular weight is 360 because someone help me measure the MW , he told me the MW is  360. but I don`t known the precision of his measure.

    In addition, should I how to do in order to deduce out the sturcture?

[Custos]

Surely there could be multiply charged ions due to the fact that it was Electrospray Ionisation?  If so, the m/z could only be a fraction of the real Molecular Mass.  (Not that i'm saying that this is the case here, it doesn't look like it to me, i'm still a little bemused as to how you get a mass of 360 and only 3 ¹H environments.)

No, electrospray is a soft ionisation technique and often the opposite is observed - only the molecular ion and no fragmentation.

If the molecular ion is 360 that should tell you that the molecule has either no nitrogen atoms, or an even number (otherwise the molecular weight would be an odd number). You also have a peak at 316 - a loss of 44 from the molecular ion - which could indicate loss of CO₂. Decarboxylation like that often indicates a carboxylic acid - this fits with the carbonyl peak in the IR.

Now because you have only a few proton environments you may have a highly saturated system and probably a symmetrical system - e.g. a couple of magnetically equivalent ethyl ester functions. Even so, 360 is quite a high molecular weight so I'd be guessing you could have some heavy atom in there (iodine, 127 perhaps?). You need a bit more info on the compound yet - a carbon spectrum and maybe some chemical tests.

[Sam (NG)]

Surely there could be multiply charged ions due to the fact that it was Electrospray Ionisation?  If so, the m/z could only be a fraction of the real Molecular Mass.  (Not that i'm saying that this is the case here, it doesn't look like it to me, i'm still a little bemused as to how you get a mass of 360 and only 3 ¹H environments.)

No, electrospray is a soft ionisation technique and often the opposite is observed - only the molecular ion and no fragmentation.

If the molecular ion is 360 that should tell you that the molecule has either no nitrogen atoms, or an even number (otherwise the molecular weight would be an odd number). You also have a peak at 316 - a loss of 44 from the molecular ion - which could indicate loss of CO₂. Decarboxylation like that often indicates a carboxylic acid - this fits with the carbonyl peak in the IR.

Now because you have only a few proton environments you may have a highly saturated system and probably a symmetrical system - e.g. a couple of magnetically equivalent ethyl ester functions. Even so, 360 is quite a high molecular weight so I'd be guessing you could have some heavy atom in there (iodine, 127 perhaps?). You need a bit more info on the compound yet - a carbon spectrum and maybe some chemical tests.

I know that electrospray is a soft ionisation technique, it can still produce multiple charges on one ion with multiple charge sites, that's what i was saying, not that it would cause fragmentation.


Iodine sounds like a good idea, you've got a loss of 127 from 332 to 205 and a peak around 500 cm^-1 in the IR.

Not sure about Carboxylic Acid, wouldn't you expect a peak at high shift in the ¹H spectrum and the peak at ~1100 cm^-1 in the IR which could be C-O is too low for a carboxylic acid, more likely to be from a secondary or tertiary alcohol or be a C-N instead.

The IR also supports primary amides with the two peaks near ~3333cm^-1 for N-H stretching, the peak at ~1690cm^-1 for C=O stretch and the peak at ~1600 for N-H bending (although on second thoughts, maybe this is a little strong for a bend and i'm just getting hung up on an idea).

[hellen]

Thanks,everyone!

I plan to elenentary analysis after "5.1". Could will the problem be dissolved? If not, could I need  what to do?

[kiwi]

if you tell us what the reaction was, you probably won't need an elemental to find out the product. what reagents and conditions did you use?

[hellen]

if you tell us what the reaction was, you probably won't need an elemental to find out the product. what reagents and conditions did you use?

The compound is not my product of my reaction. it is  the analysis of unknown compound! So there is no ways to deduce the structure  according to reaction!

[kiwi]

did it fall from the sky? is it an extract of a plant? fungi? icecream wrapper? everything comes from somewhere

[english]

Just because your unknown is a reactant does not mean you can't deduce the structure by looking at the product's structure (if known).

You can work backwards, and then validate what you've done with your spectra.

[hellen]

Oh. I extract it from  brightener.