[Serenagreene]

I'm trying to do an extraction.  I have 3 unknown organic compounds.  The first step I do (after adding an organic solvent) is to add dd H2O and I have one compound stays in the water, which is good, but what is bad is that I can't figure how to get it out of the water.  The instructions that I was using suggested letting the water evaporate, well that was a bad idea because the compound evaporate before the water did...  What would be the best way to get it out of the water?  Should I try to distill it or is there another better way?

Thanks

-Serena

[agrobert]

Saturate the water with sodium chloride and back extract so that the organic will go into ether or methylene chloride.

[barcrphd]

because the compound evaporate before the water did...  What would be the best way to get it out of the water?  Should I try to distill it or is there another better way?

your compound evaporates before water means it should have a lower boiling point. in that case distillation is the best option. why not try it and see..

[Serenagreene]

Thanks, this helped a lot.  I talked to my instructor and she told me that salting out was the usual procedure.  So I salted it out and extracted it into ethyl acetate, which turns out was not such a hot idea because there isn't a 10 degree seperation between it and my unknown (I have 3 unknowns mixed together).  Sigh, so on Friday I will attempt a Fractional distillation.  With the rest of my unknown mixture I will leave it in the water and do a simple distillation.

-Serena

[agrobert]

Thanks, this helped a lot.  I talked to my instructor and she told me that salting out was the usual procedure.  So I salted it out and extracted it into ethyl acetate, which turns out was not such a hot idea because there isn't a 10 degree seperation between it and my unknown (I have 3 unknowns mixed together).  Sigh, so on Friday I will attempt a Fractional distillation.  With the rest of my unknown mixture I will leave it in the water and do a simple distillation.

-Serena

How many compounds do you have that are water soluble?  If one, then salt it out and extract into pure organic solvent, then evaporate.  Then you should have a pure compound.  Ask more questions if you don't understand.  Fractional distillation is a waste of time and is very inefficient if you can figure out an extraction.

[Shazza2008]

Could you add salt, then extract into dichloromethane or diethyl ether (low boiling points). You could then Dufton distil off most of the solvent then pump off the remainder on a vacuum manifold at say minus 40 deg C.

Hope this helps

Shaz

[venkatjohnny]

Hi serena,
u said that your compound was water soluble, it may be a salt!!!! if it so , u can add acid or base(depends up on your compound nature) to break the salt and then u can extract with the organic solvent. Give last preference to Fractional distillation ... good luck