The extraction of compounds from these natural products is an example of solid/ liquid extraction-the solid being the natural product and the liquid being the solvent into which the compounds are extracted. In research, a Soxhlet extractor is often used for solid/liquid extraction.
Although solid/liquid extraction is the most common technique for brewing beverages and isolating compounds from natural products, liquid/liquid extraction is a very common method used in the organic laboratory, specifically when isolating reaction products. Reactions are typically homogeneous liquid mixtures and can therefore be extracted with either an organic or aqueous solvent. Organic reactions often yield a number of by products-some inorganic and some organic. Also, because some organic reactions do not go to 100% completion, a small amount of starting material is present at the end of the reaction. When a reaction is complete, it is necessary to do a workup, that is, separate and purify the desired product from the mixture of byproducts and residual starting material. Liquid/liquid extraction is a common separation step in this workup, which is then followed by purification of the product. There are two types of liquid/liquid extractions: neutral and acid/base. ...
2 CH3CH2CH2CH2OH +2NaBr +H2S042CH3CH2CH2CH2Br +2H20 +Na2S04
The 1-bromobutane is isolated from the reaction mixture by extraction with t-butyl methyl ether, an organic solvent in which 1-bromobutane is soluble and in which water and sodium sulfate are insoluble. The extraction is accomplished by simply adding t-butyl methyl ether to the aqueous mixture and shaking it. Two layers will result: an organic layer and an aqueous layer. The t-butyl methyl ether is less dense than water and floats on top; it is easily removed/drained away from the water layer and evaporated to leave the bromo product free of inorganic substances, which reside in the aqueous layer.
The extraction of a compound such as 1-butanol, which is slightly soluble in water as well as very soluble in ether, is an equilibrium process governed by the solubilities of the alcohol in the two solvents. The ratio of the solubilities is known as the distribution coeeficient, also called the partition coefficient (k), and is an equilibirium constant with a certain value for a given substance, pair of solvents, and temperature
The concentration of the solute in each solvent can be well correlated with the solubility of the solute in the pure solvent, a figure that is readily found in solubility tables in reference books. For substance C
K = concentration of C in t-butyl methyl ether
Concentration of C in water
>solubility of C in t-butyl methyl ether (g/100mL)
Solubility of C in water (g/100mL)
Consider compound A that dissolves in t-butyl methyl ether to the extent of 12 g/100mLand dissolves in water to the extent of 6g/100mL.
K = 12g/100mL