2008 student handout: liquid-liquid extraction

Summary of Procedure:

Thin Layer Chromatography is the second experiment of the 1st semester introductory sequence.

The unknown mixture of two solid compounds that was handed out last week is now separated with a series of liquid-liquid extractions.

Positive aspects of this experiment:   

+ Liquid-Liquid Extraction is a fundamental Organic Chemistry technique. This experiment allows students to practice this technique. Filtration of a precipitate and the use of a drying agent to remove water from a nonpolar solvent are other common techniques in Organic Chemistry.

+ If the 2 compounds are chosen well, the separation is relatively straightforward.

Neutral (may be positive or negative) aspects of this experiment: 

± Do not grind the two unknown compounds together, they will react with each other in some cases.

± A lot of non-polar compounds are recovered in poor yields because they get lost in the removal or water + filtration step. The drying agent can be washed with ether.

± tert-butyl methyl ether is preferred as a solvent in this case to dichloromethane because it is retained in the separatory funnel.

Negative aspects of this experiment:

- Some combinations of compounds behave differently than others. There is a certain amount of trial and error involved to determine which combinations do not work well together (difficult to separate or react with each other). For example in Fall 2008, I tried a new aromatic amine, 1-maphthylamine, it smelled pretty nasty and did not behave well at all in the separation step.

Inquiry & Extension Ideas:

● Acetanilide, despite its amide functionality, does not extract into the aqueous acid.

Data Links: 

Student Comments:

Student Comments 2007: liquid-liquid extraction

Student Comments 2008:_liquid-liquid extraction

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