Hello community,
I would like to have an efficient drying protocol of deuterated NMR solvents. Which drying agent to use ? How much do I have to use ? Do I have to wait for a certain time (24h or less) ?
Thank you in advance.
Stirring it over calcium hydride and vacuum distillation is the only way to get rid of water, and after distillation you have to put it over 4A molecular sieves for atleast 24 hour, then only you can water free DMSO-d6. I know this process is very costly but this is the only way.
Mohamed Khedawy it may work with DMSO-d6 as it has a high boiling point, but, it will not really work for solvents with low boiling point like DCM-d2. Thank you for your valuable answer.
Dear Salem, thanks for posting this interesting technical question on RG. Drying of deuterated solvents for NMR measurements requires the same drying agents than the corresponding "normal" solvents. The problem is that there is no universal drying agent which is equally suited for all solvents. OIn this context please have a look at the following useful guide:
Solvent drying and Drying agents
http://delloyd.50megs.com/MOBILE/drying.html
We normally dry solvents like THF-d8, toluene-d8 and C6D6 over sodium metal / benzophenone. For DMSO-d6 molecular sieve drying and vacuum distillation would be fine. Please note that sodium metal must not be used in combination with chlorijated solvents (CD2Cl2, CDCl3) because of the risk of explosions.
Good luck with your work and best wishes, Frank Edelmann
In extreme cases it is useful to pre-soak NMR sample tubes in D20 overnight. The tube glass surface contains interstitial water. Removing interstitial water by heating and, or vacuum treatment is inconvenient and inefficient. Extreme heat can warp high-performance (very thin) tubes.
Pre-soaking tubes in D2O exchanges the interstitial water H in with D. Later, when the interstitial D2O exchanges into deuterated NMR solvents, the water resonance amplitude is extremely low compared to untreated NMR tubes.
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