[taurean]

Can someone help me with the workup of SmI2 (samarium(II) iodide) reaction?  When I do workup with water and extract with ethyl acetate, I never see a clear separation of aqueous and organic layers in the Erlenmeyer flask.

Seeking advice from people who frequently use this reagent.

Thanks,
taurean

[Yggdrasil]

You could try adding some NaCl, which may cause the aqueous layer to separate from the ethyl acetate.

[Ψ×Ψ]

Maybe <a href="http://sanjayat.wordpress.com/2006/10/03/the-nmr-cap-trick/">this</a> will help?
Can't say I've ever used SmI₂, though.

[taurean]

You could try adding some NaCl, which may cause the aqueous layer to separate from the ethyl acetate.

I tried adding NaCl, it doesn't help.

[taurean]

Maybe <a href="http://sanjayat.wordpress.com/2006/10/03/the-nmr-cap-trick/">this</a> will help?
Can't say I've ever used SmI₂, though.

Nice trick. thanks.

[movies]

What was the solvent for the reaction?

[taurean]

What was the solvent for the reaction?

Used 0.1 M solution of SmI2 in THF.  So, I used THF as a solvent.

[DaveD]

I think whenever you are doing a work-up and don't get a good separation of the layers, it is because the densities of the two phases are very similar.  What you need to do is change the density of either the aqueous or organic phase in order to see a separation.  I think it is probably a coincidence that your SmI2 reaction didn't show a good separation - rather than this being typical of most/all SmI2 reaction workups.

Yggdrasil's suggestion of adding NaCl is one way of changing the density of the aqueous layer.  Since this didn't work for you - try an organic solvent (for example CHCl3) which has a different density than EtOAc.

THF is a powerful cosolvent of aqueous and organic layers - you may also try rotovapping off some/most of the THF prior to adding your organic solvent for work-up.  This may help, too.

[Yggdrasil]

Yggdrasil's suggestion of adding NaCl is one way of changing the density of the aqueous layer.  Since this didn't work for you - try an organic solvent (for example CHCl3) which has a different density than EtOAc.

I was under the impression that adding salt increased the ionic strength of the aqueous phase which decreases the solubility of organics in the aqueous phase, allowing the EtOAc to separate from the water.  Similarly, adding another organic solvent like chloroform decreases the polarity of the organic phase which decreases the solubility of water in the organic phase, causing the two layers to separate.  The density explanation makes sense though since having two layers with fairly different densities would allow an emulsion to separate easier.

[DaveD]

I agree that phase separations can be understood by considering the polarity of the organic phase and the ionic strength of the aqueous phase.  One of the beauties of organic chemistry -- there are many ways to look at, understand, and approach a problem.  :-)

[taurean]

DaveD and Yggdrasil,

Thanks, for some nice input.  I am going to try your suggestions.

My compound is highly polar.  Decreasing the polarity of the organic phase might create some problems with the solubility of my product.  Anyways, I will give a try.

I was reading in someone's thesis, that addition 1N HCl and sod.thiosulfate, during the workup would help.  Let me know your comments.

[movies]

Sodium thiosulfate can be used to destroy excess iodine in the workup.  It's not a bad idea to try that out.  Is it possible that your molecule is getting protonated or deprotonated and then finding its way into the aqueous layer?  Other good solvents for very polar molecules are dichloromethane and chloroform, so those might be worth a shot too.

[chiralic]

Can you change ethyl acetate by diethyl ether? and then the organic phase wash with a saturated solution of K2CO3 and a saturated solution of NaCl

[taurean]

Can you change ethyl acetate by diethyl ether? and then the organic phase wash with a saturated solution of K2CO3 and a saturated solution of NaCl

I can try that.  thanks.

[mir]

Can someone help me with the workup of SmI2 (samarium(II) iodide) reaction?  When I do workup with water and extract with ethyl acetate, I never see a clear separation of aqueous and organic layers in the Erlenmeyer flask.

Seeking advice from people who frequently use this reagent.

I havent tried this reaction, but if you dont want to change extraction-solvent (you might check up your product-solubility in Handbook), try to add a little toluene to the ethylacetate. It works very well while working on diethylether/water extraction and the phases mixes into an emulsion. If toluene is miscible with ethylacetate (I believe it is), it might work here as well. Correctly in the diethylether/toluene system, you actually get a new emulsion in the organic phase, which drastically changes the density of the organic layer.