Sciencemadness Discussion Board

extracting from dmso

overload - 4-1-2012 at 11:14

I know this sounds stupid but does anyone know if dmso containing a dissolved liquid with a freezing point of bellow -100°f can be placed in an ice bath and extracted with anhydrous toluene or ether once the dmso has frozen?

-The dissolved liquid chemical is soluble in toluene and ether.
-The extraction solvents temperature is brought down in the same ice bath used to cool the dmso before extraction.


The reason I ask is because I'm trying to simplify the work up and the clean up of a private chemistry experiment (make it easier).

DrNoiZeZ - 5-1-2012 at 07:52

why do you need to freeze it?
I think you can add some water and then extract your liquid using toluene that don't even need to be anhydrous, unless your liquid cannot be put together with water, it will hydrolise? Will it explode/decompose at rt?
The DMSO mp is about 18 Celsius if you need work below that temperature you can try to filter it and wash the filtrate with toluene (ether may be not a good choice due DMSO solubility), it may work.

overload - 5-1-2012 at 14:16

Quote: Originally posted by DrNoiZeZ  
why do you need to freeze it?
I think you can add some water and then extract your liquid using toluene that don't even need to be anhydrous, unless your liquid cannot be put together with water, it will hydrolise? Will it explode/decompose at rt?
The DMSO mp is about 18 Celsius if you need work below that temperature you can try to filter it and wash the filtrate with toluene (ether may be not a good choice due DMSO solubility), it may work.


The reason I don't want to mix with water is because I want to simplify the recycling process. The less water used the smaller the volume of liquid I need to heat to boiling (saving energy and time). Since water may effect the ability of dmso to stay crystalline I choose anhydrous conditions.

I believe its toluene that is miscible in dmso how ever it may still be used. There are many ways you can do this.

Panache - 6-1-2012 at 03:46

All the non polar aprotics suffer for this, and their relative expense, as such to remove them they need vac distilling or flooding with water and extracting. Good suggestion though unfortunately it won't work, to confirm this, try it, however i believe the dmso will simply extract into the toluene.
As for simplifying the recycling process, i know of nothing simplier than flushing it down the sink and letting the sewage plant use it's economies of scale to properly recycle the dmso. If this irks you think about flowers and meadows. If you live in a developing country with raw sewage in open sewers and no treatment facility, simply pyne for a better life whilst pouring it down the sink.
Or by a rotovap, however thats a lot of dmso worth


[Edited on 6-1-2012 by Panache]

fledarmus - 6-1-2012 at 04:44

Freezing the dmso with your sample and then trying to filter out your sample doesn't work very well. You end up with a lot of your sample stuck in the dmso crystals (dmso doesn't seem to form really nice crystals, more kind of massy ones with a lot of inclusions) and a lot of dmso washed out with your solvent.

If you really want to totally avoid water, you might try doing it the other way - dissolve your dmso sample in a relatively large volume of ether or toluene (whichever it dissolves in) and then freeze the sample until the dmso crystallizes and filter it very cold. In this case, your compound of interest is already dispersed in your solid, so the inclusions in your dmso are much more likely to be toluene or ether rather than your desired compound. Essentialy you are recrystallizing dmso and leaving the "impurity" (your desired compound) in the recrystallization solvent.

You go through lots of solvent this way though - I don't see how it's better than doing a liquid-liquid extraction in terms of solvent recovery.

overload - 7-1-2012 at 16:44

Quote: Originally posted by fledarmus  
Freezing the dmso with your sample and then trying to filter out your sample doesn't work very well. You end up with a lot of your sample stuck in the dmso crystals (dmso doesn't seem to form really nice crystals, more kind of massy ones with a lot of inclusions) and a lot of dmso washed out with your solvent.

If you really want to totally avoid water, you might try doing it the other way - dissolve your dmso sample in a relatively large volume of ether or toluene (whichever it dissolves in) and then freeze the sample until the dmso crystallizes and filter it very cold. In this case, your compound of interest is already dispersed in your solid, so the inclusions in your dmso are much more likely to be toluene or ether rather than your desired compound. Essentialy you are recrystallizing dmso and leaving the "impurity" (your desired compound) in the recrystallization solvent.

You go through lots of solvent this way though - I don't see how it's better than doing a liquid-liquid extraction in terms of solvent recovery.


I understand what you mean when you say dmso won't freeze well. I've come up with a similar method to the one you explained that I can try in the coming weeks. The way I plan to attempt this is with an ice bath that has magnetic stirring. The dmso solution is dried if possible and placed in a beaker and the beaker into the ice bath. Stir bar is added. As soon as the dmso starts to crystallize I want to add diethyl ether at a rate that causes the dmso crystals to float about freely like a snow storm tornado (forgive me). Stirring and cooling continue for a few minutes longer and then the dmso crystals are vacuum filtered from the ether through a sintered glass funnel. The funnel containing the dmso is quickly moved back to the beaker and the dmso is allowed to melt through. The beaker is weighed ect. Ether is split into portions to test different ways of neutralizing any unreacted reagents and or washing methods before the ether is distilled. Finally the liquid of interest is distilled.

I wrote this as a theory. No tests have been done yet.