12.1 Solubility-Based Methods

LEARNING GOALS

After   Chapter 12.1,   you will    be  able    to:

Recall  the conditions  required    for two solvents    to  be  used    together    in  an  extraction

Explain why repetition  is  important   in  extraction  procedures

Predict whether a   given   solute  is  more    likely  to  dissolve    in  the aqueous or  organic layer

within  a   separatory  funnel

One of the simplest ways to separate out a desired product is through extraction, the transfer of a
dissolved compound (the desired product) from a starting solvent into a solvent in which the
product is more soluble. Extraction is based on the fundamental concept that like dissolves like.
This principle tells us that a polar substance will dissolve best in polar solvents, and a nonpolar
substance will dissolve best in nonpolar solvents. These characteristics can be taken advantage of in
order to extract only the desired product, leaving most of the impurities behind in the first solvent.

KEY CONCEPT

Like    dissolves   like    is  a   fundamental concept on  the MCAT.   Remember    that    polar   substances

will    associate   with    other   polar   substances, and nonpolar    with    nonpolar.

EXTRACTION

When we perform extractions, it is important to make sure that the two solvents are immiscible,
meaning that they form two layers that do not mix, like water and oil. The two layers are