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Topic: Removal of DMF  (Read 22240 times)

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Offline whawhaxd

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Removal of DMF
« on: July 25, 2007, 10:49:21 AM »
Hi, I'm running a reaction where DMF is used as a solvent.

Reactants are 1,3-Bis(tert-butoxycarbonyl)-2-methyl-2-thiopseudourea and benzylamine.

The reaction was performed at R.T overnight.

I'm just wondering if there is a good and possibly simple way to get rid

of DMF, which has a very high boiling point.

Thank you guys!

Offline movies

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Re: Removal of DMF
« Reply #1 on: July 25, 2007, 12:22:34 PM »
My usual strategy is to add EtOAc and then wash with water about 5 times.  It works very well, but only if your molecule is not soluble in water.

Offline e.j.jamal

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Re: Removal of DMF
« Reply #2 on: July 25, 2007, 02:56:14 PM »
the suggestion u've got is good and better if u can Et2O instead to reduce the siolubility of DMF in water.
g. luck

Offline kiwi

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Re: Removal of DMF
« Reply #3 on: July 25, 2007, 05:17:02 PM »
all good suggestions so far, but instead of water, washing with a dilute salt solution (eg 5% w/v LiCl) reduces the solubility of your compound in the aqueous phase, while still allowing the DMF to dissolve

Offline Custos

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Re: Removal of DMF
« Reply #4 on: July 25, 2007, 09:21:02 PM »
Possibly too late for now, but another suggestion is to use DMA (dimethylacetamide) when the procedure asks for DMF. DMA is more expensive but it is totally miscible with water and insoluble in hydrocarbons (like hexane). So DMA is much easier to wash away then DMF if your product is soluble in hexanes.

Offline HarmlessChicken

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Re: Removal of DMF
« Reply #5 on: July 26, 2007, 01:32:51 AM »
The easiest, if most time consuming way, is to let it set in an evaporating dish overnight under a hood. The greater the surface area of the container, the quicker the solvent will be pulled off. Most effective when using small amounts of solvent (relative to the dish).

Offline whawhaxd

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Re: Removal of DMF
« Reply #6 on: July 30, 2007, 12:02:27 PM »
My usual strategy is to add EtOAc and then wash with water about 5 times.  It works very well, but only if your molecule is not soluble in water.


Thank you for answering my question, but as movies and e.j.jamal suggested.

What do u mean by "washing it with water" or "adding ethyl acetate or diethyl ether" ??

Are u guys talking about extraction using a separatory funnel??

Thank you again for trying to answer my questions :)

Offline movies

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Re: Removal of DMF
« Reply #7 on: July 30, 2007, 12:38:14 PM »
Are u guys talking about extraction using a separatory funnel??

Yes, exactly.

There is a difference between "extraction" and "washing" and it depends on which layer you keep.  If you have your molecule in an organic solvent and you want to get rid of some of the water in the organic layer, you would wash with brine and then discard the aqueous layer.  If, in another case, you had some fraction of your material dissolved in the aqueous layer and you wanted to get it all out, you would extract the aqueous layer with organic solvent to pull your compound out of the aqueous phase and into the organic phase.  You would then discard the aqueous layer and keep the organic extracts.

Offline taurean

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Re: Removal of DMF
« Reply #8 on: July 30, 2007, 10:30:37 PM »
In addition to all good methods suggested, I have one more method which usually works for my case.

After the reaction without workup, I put the reaction mixture into the silica gel column and run pet ether for couple of times.  I do not see any trace of DMF after I purify my compound.  I am not sure if it works in your case. 

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