[shon1802]

Hi, my textbook says there are several ways to break down emulsions, like adding salt or ethanol, but it doesn't explain how they break it down. I'm pretty sure that the addition of salt causes the salting-out effect, so the water molecules are forced out of the emulsion because of the electrostatic attraction to the added ions. But I have absolutely no clue about the ethanol...

[Arkcon]

Do you think the effect of ethanol is that much different?  In what ways does it interact with charged molecules and with water?

[kamiyu]

Well, in fact, the ethanol case is something contradictory to what I have actually experienced in the lab.

When there is something that mixes very well both with water and organic, emulsion occurs.

Therefore, when the separating funnel contains THF, DMF etc, phase separation is not very good.

I am not sure if the ethanol case is the same here, though

[phth]

Well, in fact, the ethanol case is something contradictory to what I have actually experienced in the lab.

When there is something that mixes very well both with water and organic, emulsion occurs.

Therefore, when the separating funnel contains THF, DMF etc, phase separation is not very good.

I am not sure if the ethanol case is the same here, though

yes it is.  Methanol is less of a problem, for example, it will phase separate if diluted in 1/2 with water(acid, base, etc) and extraction with organic solvent such as DCM, EtOAc, Et₂O....from personal experience.   Ethanol is a different story.

[NewmanProj]

If you're looking for a solution to a typical undergrad OC problem, then it looks as though it's been answered. In practicality, however, there are more ways to get passed the emulsion. Filter the mixture through a bed of celite in a fritted glass filter, or use ultrasound.

On a very large scale (1 kg), solvent removal and replacement with a less problematic solvent can work.

Cheers!

[kamiyu]

If you're looking for a solution to a typical undergrad OC problem, then it looks as though it's been answered. In practicality, however, there are more ways to get passed the emulsion. Filter the mixture through a bed of celite in a fritted glass filter, or use ultrasound.

On a very large scale (1 kg), solvent removal and replacement with a less problematic solvent can work.

Cheers!

Filtering approach agreed, I personally use silica gel though.

Solvent removal approach agreed, this is why some procedure mentioned to remove the reaction solvent such as MeOH and THF before extraction

Ultrasonic approach.....it looks it is doing the opposite (it encourages the formation of emulsion, see https://www.hielscher.com/emulsify_01.htm)

[NewmanProj]

If you're looking for a solution to a typical undergrad OC problem, then it looks as though it's been answered. In practicality, however, there are more ways to get passed the emulsion. Filter the mixture through a bed of celite in a fritted glass filter, or use ultrasound.

On a very large scale (1 kg), solvent removal and replacement with a less problematic solvent can work.

Cheers!

Filtering approach agreed, I personally use silica gel though.

Solvent removal approach agreed, this is why some procedure mentioned to remove the reaction solvent such as MeOH and THF before extraction

Ultrasonic approach.....it looks it is doing the opposite (it encourages the formation of emulsion, see https://www.hielscher.com/emulsify_01.htm)

Kamilu, I think the ultrasound approach is an example of "too little... too much". I can get some emulsions to dissipate in an ultrasound bath by sitting for 15 min. The immersion probes are far too powerful. Quite literally, I could not get a Takai reaction to go thermally, nor with ultrasound bath, but the reaction was over in 30 minutes with an ultrasound immersion probe. Your picture looks like the standard "cell disruptor" or immersion probe.

I agree, ultrasound is not better than the other two methods.