Need Help 2 Interpret NMR Analysis (2-FA NMR Included)

[Ekstasis-//7]

Hi,
I was wondering if someone could help me understand how to interpret a NMR analysis? I have seen these provided by a number of RC vendors. I know one in particular vendor posted NMR in the past was of 6-APB and those who interpreted it commented about it showing the 6-APB was quite impure and quite possibly some of the impurities looked nasty (toxic).

I'd love to be able to look at one of these and get a basic idea what it's telling me. This would be very useful as some vendors like to place their company logo watermark all over the NMR so it would not be possible to post all NMR's on bluelight for help with interpreting. Probably the length of my understanding at the moment would be interpreting a mass spectrum analysis. (Which seems to be a pretty lousy method of analysis without something else.
I've included a link to an NMR of 2-FA (2-FluroAmphetamine) as an example. I have no idea if this is relatively pure and/or what impurities this may show.
http://i53.tinypic.com/2m4cboo.jpg

While we are at the chemistry questions can I ask something else? It's probably basic but I haven't figured it out yet. What kind of bond is the HCl component attached to in an organic psychoactive alkaloid (for example something simple like amphetamine)? So far I can see pictures on Wikipedia that show a covalently bonded molecule as a HCl salt it has just a Cl atom shown separately along side it. I'm trying to figure out why there is not a HCl molecule and why it is not shown as covalently bonded? How does it attach to the freebase molecule and then in turn makes (at least some molecules) change from non polar to polar? The picture makes it look more like an ionic bond but an ionic bond this is only a bond between metals and non metals isn't it? The structural and empirical formula should be different for a freebase and for the molecule as a salt containing HCl or SO4 ect shouldn't it? I'm guessing then usually I'm looking at a structural forumla which is for the freebase as opposed to the salt?

 

[sekio]

With my meagre knowledge of NMR and a copy of Chemdraw it does look like freebase 2-FA. The higher PPM peaks belong to the benzene, and the integrals look OK (2 meta- hydrogens, 1 para- and 1 ortho-), the peak at around 5ppm is the amine, and the further downfield peaks are the less-saturated isopropyl carbons, the last peak with an integral of 3 is the methyl group.

Impurities in synthesis would either be free ammonium salts lost in the freebasing, 2-fluorobenzaldehyde, or lesser alkyl amines. Maybe the dimer. This spectrum looks pretty clear as far as I can tell, but I don't do NMR regularly, so take that with a grain of salt. It's entirely possible it shows another haloamphetamine or there are other impurities like 3-FA. Knowing what solvent was used for the NMR and perhaps a mass spectrum would be useful.

Drug salts usually exist with the amine protonated (like ammonium) and a free counterion (Most are weak bases). So technically there's "half" of the acid bonded to it, making most drug salts ionic and explaining why they are water-soluble as opposed to freebases. Basic nitrogens have a free lone pair that likes to pick up hydrogen ions.

 

[Torabora]

I think you would need a 19-F NMR or a 13C-NMR to tell that it is 2-FA but the rest fits to a ring substitued amphetamine

 

[sekio]

An elemental analysis (even a mass spec) and a higher-resolution 1H NMR with solvent information should be enough to tell if it's 2-FA.

 

[skillet]

The NMR is run in D2O, so it's probably the HCl salt, and it looks very pure. Of course the material you get is not necessarily the same as the stuff the NMR was obtained from.

The fine splitting in the aromatic peaks look like it could be from coupling to F, but it's hard to tell from that resolution. And the chemical shifts look most like those calculated for a 2-F aromatic than any of the other halogens. So it's quite likely this is a spectrum of 2-FA, but it's impossible to be certain without more information.

As for bonding, the amino group is basic and will form a covalent bond to hydrogen ions (from added acid) giving a positively charged ammonium ion. This forms an ionic bond to the negatively charged acid counterion, probably chloride in this case.

Edit: The aromatic peak shapes are very similar in this NMR of 2-fluorotoluene, though the shifts are slightly different (different molecule and solvent.)

 

[Ekstasis-//7]

It is quite obvious my chem knowledge is very limited. Thank you for your replies and your patience. I will try to read up on this more. It looks like maybe understanding NMRs is beyond my current learning. If people are willing I hope I can post a few more NMRs if there are people willing to help again with interpretation. Thank you very much.

 

[Roger&Me]

OK, am I just being a high-ass right now or shouldn't there be 3 peaks in the aromatic region of the NMR for 2-FA rather than 2 (at this resolution it just looks like a leaning doublet of pentets)? I see that there should be 3 sets of equivalent protons, not 2 -- ortho-subbed aromatics yield 3 aromatic peaks. Am i missing something obvious here or is it just a problem of resolution?

edit-- or is that just a triplet of doublets that is experiencing 2J splitting from the fluorine (also has 1/2 spin)? That could explain those funky multiplets. Anyways, it really is hard to tell just from this NMR spectrum alone.

 

[skillet]

Sure post them up, I love looking at NMR :D

Technically there should be 4 peaks, all aromatic protons are non-equivalent, they just happen to overlap into two sets. But yeah in this case it's a mess and not worth trying to interpret.

The proton ortho to the fluorine, for example, should be a double doublet, from coupling to the meta proton and the fluorine, but it could also have a small 4J coupling to the para proton... To add to that complexity, some apparently simple aromatic systems don't give first-order spectra, so full interpretation is impossible.

A 13C NMR would be useful, it's much easier to see the couplings of the various carbons to fluorine - they're all doublets, and mostly well separated.

But yeah, it seems quite likely this is an NMR of 2-FA.