Magelia
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How long can I wait before I take NMR?
Hi:
I just made my NMR and added my chloroform. I just saw the NMR machine is busy for the next two hours...
Can I afford to wait 2-3 hours before I take the NMR of my product? How about 2-3 days?
Thanks
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Ephesian
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I assume you used CDCl3
and yes, it should be fine
but if you don't want to trust me, save your sample, run a 1H-NMR. Then make a new sample and run an 1H-NMR and see if you have different resultant
peaks. My guess is that nothing will be different. Just don't F(*K with you gradient shims
[Edited on 22-10-2012 by Ephesian]
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UnintentionalChaos
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If the thing that you dissolved in the chloroform is stable, then yes, you'll be more than fine. I've left (stable) samples in NMR tubes for weeks and
as long as the caps fit tightly enough to keep the CDCl3 in (wrapping the top in parafilm helps), you're golden.
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DJF90
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I've had samples gone off in the NMR tube. Sometimes this is because the sample was light sensitive (e.g. phenylacetylene iodide), but chloroform is
quite acidic and can cause troubles sometimes. Its worth noting that CDCl3 is not the only NMR solvent available, but it is one of the most common.
Benzene-d6 often does a good job, and multiplets are often more spread apart, making asigning the peaks and multiplicities easier. It is alot more
expensive than CDCl3 but worth it in the right instances.
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Magelia
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Thanks guys. Good stuff! I'll def keep that in mind!
Regarding a C13 NMR, what's a good standard amount of time to leave my sample in the NMR machine for?
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kristofvagyok
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It depends on a lot thing, if your sample is concentrated e.g. 80mg, then the C13 scan will be good in a couple on minutes e.g. 20. But if you make a
really dilute sample with a few mg, then the whole night could be spent to get a good spectra.
And also if it is shimmed not correctly than your results could be thrown out on the window.
What NMR do you use? How much MHz? What software?
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Nicodem
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Thread Moved
23-10-2012 at 11:57 |
Magelia
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I have a 400MHz.
I just took a look at my NMR spectra and it looks HORRID. Take a look at it... was it perhaps not shimmed long enough? I left it all night...
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