[sharbeldam]

So this is the first lab of to separate organic acid/base/neutral compound which are benzoic acid/4-nitroaniline and  anthracene which are dissolved in methylene chloride [and then the lab continues by adding acid first then separating then base...etc].

The questions are:
1) which of these   solvents can replace methylene chloride?
Acetone/diethylether/Ethanol/cyclohexane/ethylacetate

Methylene chloride is more dense than water so the organic phase would be the lower phase in the funnel, so technically diethylether can be used but it would give the upper phase as the organic phase no?

Acetone and ethanol? I dont think so since they are miscible with water.
Cyclohexane and ethylacetate? Im not sure, i can not see why not? and if someone could tell me if they can replace it, would they give upper phase or lower phase as aqueous layer?

Thank you, i do appreciate it

[AWK]

If you want to use the extraction method, the solvent should not dissolve or mix with water. Ethyl acetate dissolves in water about 8g / 100g water, so it will cause more work. In addition, it hydrolyzes relatively quickly under the influence of NaOH.

[sharbeldam]

Thank you, so only cyclohexane and diethylether?

[AWK]

diethyl ether 6.5 in 100 g of water, 1.5 g water in 100 g ether, low boiling point - better to avoid.

[sharbeldam]

AWK, better to avoid because of water solubility or low BP or both?
What solubility in water specifically would rule out the solvent? Im confused because online it says its a perfect solvent for extraction but other sites say that more than 1g/100ml of water is considered water soluble (0.1-1=slightly soluble)

So it should be water soluble as you said and it has low BP, why does it say its a perfect solvent for extraction?

[AWK]

Based on my reasons, ethyl ether is not suitable for liquid-liquid extraction in the laboratory. Unless someone is more interested in sniffing the ether for a long time? Working with ether needs a temperature as low as possible (as close as possible to 0°C, neutralization of acid and base evolves some heat!), and this significantly reduces the solubility of the compounds and increases the amount of solvent several times.

http://www.thermopedia.com/content/752/

[sharbeldam]

Okay I get that but what about the solubility (thx for your patience btw), I have Benzoic acid, Nitroaniline and anthracene, so I need an extraction solvent that is not miscible in water so it can contain my organic layer that's the first condition, the second condition is that my 3 molecules need to be soluble in it Right?
So we ruled out Ethyl acetate/Ethanol/acetone for being miscible in water
We rule out ether cause of low BP.
We are left with cyclohexane as the only other option from the question, just to verify, since cyclohexane is not polar, will benzoic acid and 4-nitroaniline dissolve in it? basically if i understand right we need a solvent that can't produce hydrogen bonds with water but at the same time a bit polar so it can dissolve polar compounds like benzoic acid and nitroaniline so cyclohexane would be much less good than DCM. am i right?

THANKS

[AWK]

By far the least soluble substance in all solvents will be anthracene. Methylene chloride is the best choice for solvent among those listed by you. The solubilities of these compounds in cyclohexane will be slightly smaller, I expect about 1 g for the first two compounds and ~ 0.5 g for anthracene per 100 g of solvent. Probably the fastest separation method would be to boil a solid mixture in water, separate anthracene, and after evaporation to smaller volume, split aniline and benzoic acid from the organic solution by alkalization or acidification.

[anonymous10012]

Hi,

I assume this is just an Organic I or II lab. I think they are just looking for you to choose a polar solvent that is immiscible with water. Your logic for excluding methanol and acetone because of their complete miscibility is perfect. Ether and cyclohexane are nonpolar, so again, logical to exclude.

I used EtOAc and DCM quite interchangeably when doing organic synthesis as an undergraduate researcher.

As for the solvent solubility in water, you always dry the organic phase with a very hygroscopic compound like magnesium sulfate before evaporating solvent.

In my opinion the other replies you have received are overthinking it.

Good luck!