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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: kdog3682 on February 06, 2014, 01:53:35 PM

Title: liquid-liquid extraction question ... a little confused.
Post by: kdog3682 on February 06, 2014, 01:53:35 PM

Compound X is twice as soluble in toluene as it is acetone and is only sparingly soluble in water. Compound Y is soluble in water and acetone, but only sparingly soluble in toluene. You are given a solid mixture of X and Y. How would separate X and Y using liquid-liquid extraction?

Is the answer as simple as it seems and to simply dissolve it in toluene? Or should you dissolve it in a 50 – 50 mix of water and toluene.

I was also thinking, would it be better to dissolve it in napthalene since that's even further from acetone?

Thanks.

Title: Re: liquid-liquid extraction question ... a little confused.
Post by: kriggy on February 06, 2014, 02:29:54 PM

Yes I would dissolve it in toluene, then dissolve in water what cant be dissolved in toluene. You still would have some of the compound X in water part and Y in toluene so you can then wash the water part with toluene and vice versa.
Im not sure about dissolving in naphtalene. Might work, might not.

Title: Re: liquid-liquid extraction question ... a little confused.
Post by: PhDoc on February 08, 2014, 01:55:35 PM

.                       Toluene     Acetone/Water
Compound X            *
Compound Y                              *

If you had compound X in toluene while having compound Y in acetone/water, would you need to separate them?

This "problem" applies to a solid-solid, solid-liquid, or liquid-liquid mixture that can be partitioned between two nearly immiscible phases.

Toluene is miscible with acetone. Acetone is miscible with water. Acetone and water when mixed together experience strong dipole-dipole interactions that cannot be overcome by toluene. Hence if you take your mixture, then dump it into a separatory funnel containing the three solvent system, compound X will be in the upper phase (toluene, d = 0.87) while compound Y will be in the lower phase (acetone-water, d = 0.93 for 1:1 mixture 20C, J. Chem. Eng. 1965, 10(4), 330-334.). Be prepared for a really nasty emulsion with this one. In principle this works, however I wouldn't want to do it in the lab.

When it comes to something like this, it's easier to concentrate on images rather than words. The words sometimes lead to confusion.

Title: Re: liquid-liquid extraction question ... a little confused.
Post by: curiouscat on February 08, 2014, 03:21:46 PM

Why not just add water, filter & then evaporate off water?