[friedpork]

I will be performing a liquid-liquid extraction of an unknown mixture. The mixture will consist of two compounds - one neutral and one acid. I need to decide which solvents I should use in order to perform the liquid-liquid extraction the best. The solvents I will be testing are Diethyl ether, water, 10% aqueous HCL, 10% aqueous NaOH, 5% aqueous NaHCO3.

I know that the first solvent should completely dissolve both compounds in the mixture. The second solvent should be immiscible with the first solvent and the should only be able to dissolve only one component of the original mixture.

How do I know which solvents are immiscible with each other and which solvents am I probably most likely to use?

[Arkcon]

You can simply look up the solubility in the appropriate reference, but there's something else you should look into.  Why are you given a "neutral" and an organic acid?

[friedpork]

The purpose of the experiment is to be able to separate the neutral compound and organic compound within the mixture. We are not given which neutral compound and acidic compound we will be working with. We have to determine ourselves what those compounds actually are.

[discodermolide]

Ether is not miscible with water or salt solutions.
Think about the chemistry going on, does a neutral compound react with 10% NaOH solution, does an acid react with 10% NaOH solution? Or the 5% bicarbonate solution.
Does an acid react with 10% HCl does a neutral compound react with 10% HCl solution?

[friedpork]

Well the acid should react with either the NaOH or the NaHCO3. So the HCl is pretty much out of the question. Hopefully the ether will react with both compounds which makes the liquid-liquid extraction easier since the top layer would be the ether and the bottom layer would be the aqueous solution.

[discodermolide]

The ether will not react with anything, it is a solvent.
When I asked you the questions I was referring to your unknown mixture containing a neutral compound and an acidic one.
How will they react with the reagents?
Remember you have to separate these two compounds.

[friedpork]

What I meant to say for the ether was that the ether should likely dissolve both compounds since very many organic compounds are soluble in diethyl ether. I can dissolve both compounds in the ether and probably separate the acid by adding either the NaOH or NaHCO3.

[discodermolide]

Ok you are on the right track.
Keep going.

[friedpork]

ok well, if I add the NaOH or NaHCO3 I'm left with the salt?? So I think I have to get rid of the salt with some sort of acid I believe which probably will be supplied in the lab that day.

[discodermolide]

OK you have dissolved your compounds in ether and wash the ether solution with base to give the neutral compound and the salt of the acid. In which phase is the neutral compound and which phase contains the salt of your acid?

[friedpork]

I'm not exactly sure what you mean by saying which phase the neutral compound is in and which phase my salt is in. I think you mean that the salt of acid is suppose to be in the aqueous solution and the neutral compound should be in the ether? Since water is denser than the ether that means the salt should be on the bottom and the neutral compound should be on top. Is this what you were asking?

[discodermolide]

Yes, the neutral compound is in the ether and the salt of your acid is in the water layer.
Separate the layers. Evaporate the ether and you have the neutral compound.
Re-acidify the water layer with the HCl and your acidic compound should precipitate out if it doesn't then re-extract it with ether.

[friedpork]

Yes I think I got it. This experiment is a 3 parter where the first part is separating the layers. Then I have to recrystallize and find the melting points of the two compounds as well. I'll probably need help determining the solvents for the recrystallization part but until then thanks for your help. =)

[discodermolide]

Glad to help