Molecular weight as a means of identifying a compound

[J Hicks]

Hi all,

I am conducting research into photo-protection of human skin to prevent skin damage. I have received a promising small molecule compound from a Chinese supplier and I have conducted some basic tests to check if it is in fact the correct substance. So far, I have received a HPLC analysis and also an independent mass spec, which seems to match the target compound (see below).

Do you think is it also necessary to have a NMR analysis to confirm the structure?

In other words, is it possible that the compound I have received could be 'structurally incorrect', despite having the same mass as the target compound? Any help or comments to answer this question would be welcome, I am attaching the data I have on the compound to this thread and further information on the substance can be found at the following link:

https://medkoo.com/products/15235

 

Mass Spec

 

HPLC

 

Edited March 27, 2018 by J Hicks

[hypervalent_iodine]

I would get a 1H NMR and match it to literature. Personally, I probably wouldn’t have bothered with low res mass spec (or HPLC if it’s for use in synthesis) if all you’re doing is confirming the structure of a commercial product for later use, and if that product has already been characterised; 1H NMR is a better tool for comparison in that case. 

[J Hicks]

Thanks for your reply. Does this mean then, that the substance I have received could be structurally incorrect despite the test results noted above?

[hypervalent_iodine]

17 minutes ago, J Hicks said:

Thanks for your reply. Does this mean then, that the substance I have received could be structurally incorrect despite the test results noted above?

 

You can say that it’s pure, and that something with that mass is in your sample, but mass spec - particularly low res mass spec such as what you have used - isn’t something I would rely on by itself for structural confirmation / characterisation (even if it gives you what you want).  I’m sure it is correct, but if you want to be completely sure then I’d get an NMR. 

[J Hicks]

Thank you, so I assume from your comments that it is a possibility that the substance I received is structurally incorrect, despite having those test results.

[hypervalent_iodine]

29 minutes ago, J Hicks said:

Thank you, so I assume from your comments that it is a possibility that the substance I received is structurally incorrect, despite having those test results.

 

Unlikely, but always possible. If you are using this compound directly in testing, I would do a full suite of characterisation anyway. If it’s for synthesis, you can probably take your results as a reasonable assurance and go on as is (though in future, I would go for NMR over LRMS). You’ll be characterising whatever you make anyway, if that’s what you’re doing.

[John Cuthber]

It is certainly possible to have the same mass and yet be a different compound.
That's easy if the materials are isomers and still possible, even if they aren''t.

 

NMR or IR would help

Ironically, if you have an authentic sample then melting point will give you a very clear indication of purity.

(of course, many compounds decompose without melting, in which case it won't work)

[J Hicks]

So I had an NMR done on the compound, but now I'm trying to make sense of it. I've attached the files. Can anyone help me understand if what this NMR means. 

This it's the compound that it's supposeded to be:

https://medkoo.com/products/15235

Any thoughts would be greatly appreciated.

 

BCJ-5279_1H_2.pdf

BCJ-5279_1H.pdf

[hypervalent_iodine]

Have you looked up literature NMR?

[J Hicks]

Literature NMR? Is that a catalogue of how the compound should look in an NMR? I don't know where to access that data.

[hypervalent_iodine]

No, it’s the NMR of the compound reported in scientific literature. Are you familiar with Reaxys or SciFinder? 

I also have to ask, is this work of yours a backyard job or something you’re doing as part of an actual research group? 

[hypervalent_iodine]

I would suggest looking through this https://patents.google.com/patent/WO2018009544A1/en