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Analysis of 2C-E

A

apsig

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Feb 18, 2011
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I have a batch of 2C-E I'm interested in having analyzed.

Two questions:

Would I get more/better information from HPLC purity testing or from an NMR analysis?

Which solvent is appropriate? I would assume either D2O or CDCl3 would work. Is this incorrect? 2C-E has fairly good solubility in water, but are there other considerations at work here?
 
1H-NMR will tell you what compound you have as long as the compound is pure
HPLC will tell you if you have a mixture and how many compounds are present in the mixture, but not necessarily what they are

I would go with CDCl3 with the 1H-NMR, you don't need hydrogen-absent solvents for HPLC
 
nuke said it. However the solvent depends on whether you have a salt or the freebase. Deuterated water would be a better choice for the salt IMO.

Do you know how its been purified? Even heavily cut substances can appear pure in an NMR spectrum if the aldulterants are invisible in proton-NMR.
 
I suppose it would have been pertinent to point out that what I have is the hydrochloride salt. My mistake for the omission. Heavy water it is, then.


In regards to purification, I am unsure what method was used, though it was likely just a recrystallization, which could leave in a number of contaminants with similar solubility profiles. The vendor claims 99.8% purity, a number I an HIGHLY skeptical of. That said, I don't suspect any cuts were used; I'm more interested in the possibility of precursors being present in the product.

Using integration of the curve generated, should it be theoretically possible to determine the percent of 2C-E in the sample? My apologies, I am relatively unfamiliar with NMR....
 
Integrated results on a HPLC are usually enough to get a rough idea of purity (+/- 5 or 10% in the worst cases), though it won't tell you exactly what you have (it just does a seperation). NMR will not seperate mixtures and will only give you a clean spectrum if you give it a pure substance.
 
Thank you all for the clarification. I supposed I had rather naively assumed that NMR was a magic bullet for quantification and determination of primary and contaminant structures.
 
Proton NMR can be used for estimating the purity of the sample if there is only very few impurities and you can unambigously identify what the impurities are.

You can be lucky to identify an impurity with NMR, but that can be quite tricky if its not a common solvent or something like that. You can try finding signals in the spectrum which cannot be attributed to 2C-E, but its not always possible to identify the impurity this way. Especially if you are not entirely certain which reagents were used.
 
I'd rather recommend (deuterated) DMSO as NMR-solvent. Usually it dissolves salts, too, but in contrary to heavy water you still see exchangeable protons (NH2, NH3+, OH, ...). In other words, a NMR-spectrum in DMSO will give you more information.
If you expect "only" side-products or precursors of the synthesis as impurities, then NMR is capable of verifying them, too. Sensitivity depends on the strenght of the magnetic field; with a 400 MHz-device you can still see impurities in the range ~0.5%, if shimming and calibration are done accordingly.
 
if you have the salt, you cannot inject it to the HPLC straight away, as HPLC is not able to process salts.

sure, DMSO can be used to dissolve salts aswell, even though sticking to CDCl3 is usually more convenient, because the respective database is bigger, which could facilitate the identification of impurities.
 
...then again is it next to impossible to get a salt dissolved in chloroform, in particular if the molecule is as small as 2C-E (ie. the charge-to-size-ratio is comparably large).
 
mysticgreen said:
if you have the salt, you cannot inject it to the HPLC straight away, as HPLC is not able to process salts.
Click to expand...

I'm not sure I understand what your saying by "straight away".

Of course someone can't inject a solid material of any sort, including salts, into an H.P.(Liquid).C, it only processes liquids.

But also of course someone can just easily dissolve the 2C-E salt directly into water (or aqueous mobile phase) and directly inject that salt solution into HPLC analysis. So, yes, salts can be injected straight away after solvation in water or buffer.

Even mass specs, which are not supposed to have heavy salt loads easily and routinely analyze salts at the low concentrations encountered for identification.

I have seen plenty of data from the HPLC-MS analysis of salts. Typically the counter-ion is so small that it elutes in the void volume, while the analyte of interest is retained for separation.
 
as a person speaking with some xp with LC-MS these are usually done in buffered MeCN/H2O solutions with amines being protonated i.e. salt or freebase doesn't really matter.
For NMR DMSO-solutions give the NH+ protons but usually fuck up the side-chain protons so I usually get both DMSO and CDCl3 spectra when possible (usually 13C-NMR in DMSO though, because solubility of HCl-salts is low in CDCl3)
 
Hyperthesis said:
...errrrrr, what?
Click to expand...

what waterwalker is saying is basic practical NMR , in non exchangeable solvents, the NH2 nitrogen protons split the vicinal CH2 side chain protons in irritatingly complex ways making a mess. The viscosity of D6 DMSO is also a problem.
 
DMSO-d6 is commonly used in my place; first choice due to its superior dissolving properties, to be honest. I never experienced any difficulties with DMSO-spectra (...and I've seen some, yes, Sir), but I see your point regarding the viscosity. Seems to be only an issue with special applications, though. Apart from that is CDCl3 a non exchangeable solvent, too, not?

Time to rethink some details on my side...
 
Hyperthesis said:
DMSO-d6 is commonly used in my place; first choice due to its superior dissolving properties, to be honest. I never experienced any difficulties with DMSO-spectra (...and I've seen some, yes, Sir), but I see your point regarding the viscosity. Seems to be only an issue with special applications, though. Apart from that is CDCl3 a non exchangeable solvent, too, not?
Time to rethink some details on my side...
Click to expand...

solvents used here are CDCl3 for general use CD3OD useful for a lot of the more polar stuff particularly with a small amount of NaOD, and D2O for salts, occasionally CCl4 is useful too as is TFA DMSO is used pretty much only when things won't dissolve. Obviously unless they are freebase amines don't dissolve in CDCl3 and freebasing them is quite a few extra few steps (basify, extract dry remove solvent replace solvent)

I have only ever seen splitting with the protons vicinal to amine salts in D6 DMSO it also does it with alcohol OH's,

DMSO viscosity is annoying when you have close peaks and if you can get it to dissolve in something else instead then the spectrum (half height line width) will almost always be better, it is also a major problem if the compound under investigation is a hydrate, on the plus side DMSO is very cheap and a good solvent.
 
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