[RaInBowDaSh1488]

Howdy, I've been having a bit of a problem with a reaction I am running using DMSO as the solvent. Usually DMSO doesn't give me many problems, aside from resulting in more tedious workups.

The current reaction I am running in DMSO is a bit of a different case though. The products BP is fairly low, so I can't remove the DMSO under vacuum/heating. The product also reacts with silica to a degree, so I can't practically run the product through a silica plug with a very polar solvent.

I've been trying vanilla solvent extractions, adding water to the DMSO and extracting with ethyl ether. The problem is, I can't seem to find a medium in this extraction. I either end up getting very poor recovery or having residual DMSO.

Does anyone have any suggestions? I've been doing 4x 20mL extractions with ether. The solution of DMSO/water is about 10mL. The compound I am trying to extract is a low MW azide. 

[zsinger]

Have you tried HMPT as the solvent?  I'm not exactly sure why, but that solvent seems to help me always.  Smidgen expensive…..but hey….

[Dan]

Try brine instead of water, you should get less leaching of your product into the aqueous.

[Archer]

Have you tried HMPT as the solvent?  I'm not exactly sure why, but that solvent seems to help me always.  Smidgen expensive…..but hey….

Do you mean Hexamethylphosphorous triamide or hexamethylphosphoramide (often referred to as HMPA)?

Both (confusingly) use the same acronym.

[orgopete]

We used to use a mixture of ether/hexane to reduce the DMSO extraction.

[zsinger]

Archer,
Triamide is what I meant.  I don't know why they are represented by the same letters!  Not sure exactly why, but that solvent makes finicky reactions seem to work better in all phases.

[Doctor T]

I have found that it is easier to extract the DMSO from the organic layer, rather than try to extract your product out of the aqueous layer, bringing DMSO along with it.

I would dilute the product into ~200 mL of ether and then extract the ether layer 4 - 5 times with 10 -15 mL or so of water (I'm not sure what scale this reaction was on or how much DMSO was used, so you may have to adjust the volumes accordingly), then wash it once with brine.

Hope this helps!

-T

[chenchen]

first I have to mention that azides are toxic and explosive.

You mentioned that your product has a very low bp. Why not distill your product while put your receiving flask in acetone/dry ice bath? This may help you collect more product on larger scales, but it's still a little bit tough on your scale. Keep in mind that distilling pure azide is dangerous.

Good luck!