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NMR Chloroform
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Topic: NMR Chloroform (Read 4447 times)
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Messi
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NMR Chloroform
«
on:
October 22, 2012, 02:11:55 PM »
Hey guys,
How long can I leave my sample in chloroform before I put it in the NMR machine? Is it OK if I leave my sample in there for 2-3 hours then take the NMR of it?
How about 2-3 days?
Thanks!
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discodermolide
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Re: NMR Chloroform
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Reply #1 on:
October 22, 2012, 02:14:46 PM »
Chloroform has a tendency to decompose to produce HCl and even phosgene. That's why the bottle has silver wool in it to help prevent this.
So 2-3 hours is OK but 2-3 days probably not. You can check this by NMR of course.
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Babcock_Hall
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Re: NMR Chloroform
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Reply #2 on:
October 22, 2012, 02:54:50 PM »
Some compounds degrade on their own; others react with some NMR solvents. I have synthesized one that seemed to react with DMSO, but I did not fully characterize the process.
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OC pro
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Re: NMR Chloroform
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Reply #3 on:
October 22, 2012, 03:59:12 PM »
For most of the compounds they are ok even for several weeks in the NMR tube. When I did PhD we had to wait sometimes for more than a week to get a 1H and 13C spec. I never saw any degradation in CDCl3. And I worked with highly sensitive pyrrole compounds.
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Messi
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Re: NMR Chloroform
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Reply #4 on:
October 22, 2012, 05:09:45 PM »
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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OC pro
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Re: NMR Chloroform
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Reply #5 on:
October 22, 2012, 05:13:44 PM »
Depends on the machine and of course sample amount. I you have enough material and use 50mg+ for 13C then ~100 scans should be ok. But for normal 10-20mg samples I would do at least make 1024 scans (~2h) for 13C and DEPT. So ~4h altogether.
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Messi
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Re: NMR Chloroform
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Reply #6 on:
October 22, 2012, 09:44:53 PM »
Boy oh boy is your guys' help invaluable! You guys are simply awesome!
Thanks OC Pro!
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