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Topic: Extraction of product form water/acetone  (Read 872 times)

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Offline Jfalken

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Extraction of product form water/acetone
« on: October 24, 2021, 07:11:01 AM »
So I have this product, which was supposed to me non-soluble in water (talking less than 1mg/L).
The final procedure involved acetone as solvent, so once the reaction was completed I used water in excess cause the idea was to filter off all of the water soluble impurities while the product was supposed to remain on the buchner funnel.
However, the product remained dissolved in the water/acetone mixture so the idea now is to extract the less polar product from the mixture.

I am thinking that a non-polar solvent, such as DCM or benzene would be able to extract the product into the organic phase but I am concerned about the acetone.
Will the acetone stay in the H2O due to hydrogen bonding or will I get a third layer in between the DCM and H2O where the acetone will be?

Offline Orcio_87

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Re: Extraction of product form water/acetone
« Reply #1 on: October 24, 2021, 09:59:43 AM »
Acetone is miscible both with the water and CH2Cl2, I think it can form some form of the emulsion.

Offline rolnor

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Re: Extraction of product form water/acetone
« Reply #2 on: October 24, 2021, 11:58:01 AM »
I would try DCM, you will have 2 layers, not 3. If its hard to get separation you can add more water.

Offline Jfalken

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Re: Extraction of product form water/acetone
« Reply #3 on: October 24, 2021, 05:01:25 PM »
Acetone is miscible both with the water and CH2Cl2, I think it can form some form of the emulsion.

What solvent should I try then to be sure I  get all the product into the organic phase if not DCM?

I would try DCM, you will have 2 layers, not 3. If its hard to get separation you can add more water.

Will the acetone go into the DCM or stay in the aq phase?

Offline rolnor

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Re: Extraction of product form water/acetone
« Reply #4 on: October 24, 2021, 06:02:34 PM »
It will be in both phases.

Offline kriggy

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Re: Extraction of product form water/acetone
« Reply #5 on: October 25, 2021, 08:41:26 AM »
Adding water to water miscible solvent for workup often times produce more trouble than its worth. I would evaporate first next time.

You can try to concentrate your solution on rotovap anyway followed by extraction. If thats not what you want to do, adding enough salt will make the water and acetone separate.

Offline rolnor

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Re: Extraction of product form water/acetone
« Reply #6 on: October 25, 2021, 09:47:18 AM »
The product has very low solubility in water so adding more water is no large issue if you ask me. It does depend in how large volume we talk about offcourse. Its not so easy to evaporate water so this would not be my first choise.

Offline Jfalken

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Re: Extraction of product form water/acetone
« Reply #7 on: October 26, 2021, 02:43:38 AM »
It will be in both phases.

So what if I first rotovap the mixture, could I then get rid off the excess acetone in the water or will the hydrogen bonding between the acetone and the water make it too hard to evaporate the acetone?

Adding water to water miscible solvent for workup often times produce more trouble than its worth. I would evaporate first next time.

You can try to concentrate your solution on rotovap anyway followed by extraction. If thats not what you want to do, adding enough salt will make the water and acetone separate.

Yes, I learnt it the hard way now.
If I rotovap the acetone off, it would be just water and in theory I should be able to filter off the product.
But what was strange was that I had about 1 liter acetone, and then added 2 liter water and it was still not enough for the product to precipitate out.

Could you explain the addition of salt a  bit more and why it makes the product precipitate?

The product has very low solubility in water so adding more water is no large issue if you ask me. It does depend in how large volume we talk about offcourse. Its not so easy to evaporate water so this would not be my first choise.

Maybe if I first give it a go with evaporation, if that can get some acetone out of the mixture, followed by a DCM extraction, followed by a evaporation?
Could try it and see what happens, if I will be able to rotovap off some acetone initially.


Offline rolnor

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Re: Extraction of product form water/acetone
« Reply #8 on: October 26, 2021, 03:45:15 AM »
First you can work with a small part of the solution, say 100ml. You could try to dilute this with more water to see if your product precipitates. If it does not its a good idea to evaporate, acetone will evaporate first then you will probably get a azeotrope mixture that evaporates. Have you run TLC on the solution? It would be nice to see if you have any product so you dont waste time and effort.

Offline Jfalken

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Re: Extraction of product form water/acetone
« Reply #9 on: October 29, 2021, 01:26:49 AM »
First you can work with a small part of the solution, say 100ml. You could try to dilute this with more water to see if your product precipitates. If it does not its a good idea to evaporate, acetone will evaporate first then you will probably get a azeotrope mixture that evaporates. Have you run TLC on the solution? It would be nice to see if you have any product so you dont waste time and effort.

That is a good idea, since 2:1 ratio of water/acetone was not enough I can try 100mL of the mixture and add an other liter of water to see if it precipitates out.
I havent, but that is a good idea!
Although I can see that the water/acetone mixture is somewhat goldish in color, so it should be there.
Just have to figure out a good eluent system. See if I can post the pictures from the TLC chamber here later.

Offline rolnor

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Re: Extraction of product form water/acetone
« Reply #10 on: October 29, 2021, 06:13:42 AM »
If you post the structure I can suggest a eluent mixture.

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