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Author: Subject: Removal of DMF (Dimethylformamide)
Godrick VanHess
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[*] posted on 15-2-2018 at 09:07
Removal of DMF (Dimethylformamide)


So I have a sensitive indole dissolved in DMF and I need to remove the DMF. I can evaporate the DMF using a rotary evaporator at 60°C which is unfavorable for my application. I am thinking about trying to form a lower boiling azeotrope and try and evaporate that. I have found a few sources that mention using benzene, toluene, heptane or a potential mixture of these to for said azeotrope. I was going to try using benzene - DMF azeotrope but I would like to find an even milder method if possible. Does forming an azeotrope sound like a good idea or does anyone have a better idea short of finding a different solvent?
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[*] posted on 15-2-2018 at 09:57


DMF is water miscible. If you add enough water and after that an aprotic solvent after that, like dichloromethane, with stirring, DMF will be mixed at the water layer and the indole will be remained dissolved at the dichloromethane layer.

Then, it's just to fractionate the layers and distill off the dichloromethane bottom layer at vacuum, with no heat at all, to don't screw up your residual indole.
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Dr.Bob
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[*] posted on 15-2-2018 at 11:57


Good luck, DMF is tough to get off, azetropes might help a little, but a higher vacuum will help a lot more. And if you use DCM, I have always found that it hold a good bit of DMF from water, so you miught get rid of some, but not all. I always try to rotovap off as much as possible first under the highest vacuum I can get, then do a water workup, preferably with EtOAv or ether, which don't hold DMF as well, then evaporate and remove the last DMF on the high vacuum overnight or 2 days. That usually works for me.
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Godrick VanHess
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[*] posted on 15-2-2018 at 13:51


Quote: Originally posted by Dr.Bob  
Good luck, DMF is tough to get off, azetropes might help a little, but a higher vacuum will help a lot more. And if you use DCM, I have always found that it hold a good bit of DMF from water, so you miught get rid of some, but not all. I always try to rotovap off as much as possible first under the highest vacuum I can get, then do a water workup, preferably with EtOAv or ether, which don't hold DMF as well, then evaporate and remove the last DMF on the high vacuum overnight or 2 days. That usually works for me.
Ah, yes that could explain it! We did try extracting into DCM but the DMF apparently always appears on the NMR spectra. Unfortunately I'm stuck with the vacuum. I think I might try extracting into a different solvent also. Did you mean EtOAc or EtOAV? (Sorry, just want to make sure I'm on the same page)


[Edited on 15-2-2018 by Godrick VanHess]
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