During extraction experiments, two compounds can be separated from each other by utilizing their solubility in two immiscible solvents. The solvents are separated from each other because they each have their own density. Therefore, the one with the larger density, would be the bottom layer. Acid-base extraction utilizes acid-base reactions to alter the solubility of the acidic or basic compounds in the solvent in order to separate them. During this lab, water is used as the aqueous solvent for the unknown carboxylic acid. Tert-butyl methyl ether (TBME) was the either used that would contain the neutral compound. The unknown carboxylic acid is highly soluble in the ether layer, therefore a base, NaHCO3,was added to the carboxylic acid to form a carboxylate which is water soluble and ether insoluble. This separates with unknown neutral organic compound to the either layer as they both have low polarity and the unknown carboxylate which are both polar. Because the water layer is denser, it would be found in the bottom of the test tube with the two solutions. With the two layers determined, they can be separated and purified. For the organic layer, some residual water can be found in the layer so NaCl is used to backwash the solution and remove any aqueous waste. In addition, a drying agent, CaCl2, removes the last of the water. In the aqueous layer containing the unknown carboxylate, HCl is used to turn the basic layer back into the carboxylic acid. Both solutions utilize recrystallization to purify them.
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