Fundamental Organic Chemistry

Distribution Coefficients:
When a compound is shaken in a separatory funnel with two immiscible
solvents, such as water and diethyl ether (CH 3 CH 2 OCH 2 CH 3 ), the compound
distributes itself between the two solvents. Some dissolves in the water and some
in the ether. How much solute dissolves in each phase depends on the solubility
of the solute in each solvent. The ratio of the concentrations of the solute in each
solvent at a particular temperature is a constant called the distribution
coefficient or partition coefficient (K).
Concentration in solvent 2
K = ---------------------------------
Concentration in solvent 1
Where solvent 1 and solvent 2 are immiscible liquids.
Steps in extraction:
1) Preparation of the separatory funnel.
2) Adding the liquids. Be sure the stopcock is closed.
Safety Note:
Never add a volatile solvent to a warm solution. If you are using a
flammable solvent, make sure there are no flames in the vicinity!
3) Mixing the layers.
Insert the stopper and, holding the stopper in place with one hand, pick up the
separatory funnel and invert it. Immediately open the stopcock with your other
hand to vent solvent fumes or carbon dioxide. Swirl the separatory funnel gently
to further drive off solvent vapors or gases.
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