March 29, 2024, 10:24:49 AM
Forum Rules: Read This Before Posting


Topic: liquid-liquid extraction question ... a little confused.  (Read 3045 times)

0 Members and 1 Guest are viewing this topic.

Offline kdog3682

  • Regular Member
  • ***
  • Posts: 11
  • Mole Snacks: +0/-0
liquid-liquid extraction question ... a little confused.
« 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.

Offline kriggy

  • Chemist
  • Sr. Member
  • *
  • Posts: 1519
  • Mole Snacks: +135/-16
Re: liquid-liquid extraction question ... a little confused.
« Reply #1 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.

Offline PhDoc

  • Full Member
  • ****
  • Posts: 133
  • Mole Snacks: +22/-0
  • O-Chem Prof
    • PH.D. Organic Chemistry Tutor
Re: liquid-liquid extraction question ... a little confused.
« Reply #2 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.
O-Chem Prof

Offline curiouscat

  • Chemist
  • Sr. Member
  • *
  • Posts: 3006
  • Mole Snacks: +121/-35
Re: liquid-liquid extraction question ... a little confused.
« Reply #3 on: February 08, 2014, 03:21:46 PM »
Why not just add water, filter & then evaporate off water?

Sponsored Links