SEPARATION OF COMPONENT MIXTURE
Liquid-liquid extraction is one of the most used methods for isolating an organic compound from a mixture. This technique is commonly used to isolate and purify products from chemical reactions and is also used to isolate natural products. The process can be categorized into two types of liquid-liquid extraction. The first type takes advantage of the polarity of compounds and uses water to extract or “wash” an organic mixture by removing highly polar materials, such as inorganic salts, strong acids or bases, etc. Second, acid and base extraction, takes advantage of chemical properties of compounds.
Acid extractions are intended to separate basic compounds from an organic mixture. Organic bases, amines, are converted to their corresponding cationic salts by reacting with acids. These salts are then soluble in water and can be separated from the organic mixture.
Base extractions have a concept similar to acid extractions. They are intended to separate acidic compounds from an organic mixture. Organic acids, carboxylic acids, are converted to their corresponding anionic salts by reacting with bases. These anionic salts are usually soluble in water and can be extracted from the organic mixture.
Purpose: In this experiment you will be given a three-component mixture, an acid (benzoic acid), a base (ethyl- 4-aminobenzoate) and a neutral organic compound (9-fluorenone). You will have to separate these three compounds individually from the mixture.
benzoic acid ethyl-4-aminobenzoate 9-fluorenone
The key success for this experiment is to understand the chemical reactions that are taking place at each step of separations. You will have to fill in the blank the products that result from the chemical reactions.
Required reading: Mayo 94-108, B&F sections 4.1-4.2
What are the compounds in the top organic layer? __________________________
What is the compound in the bottom aqueous layer? __________________________
Why did you add the 6M NaOH? _________________________________
What is the compound in the organic layer? _____________________________
What is the purpose of washing the organic layer with 1 mL of water?_____________________________________
What are the two main compounds that present in the solution B? ___________________________________________________
Write the reaction (steps 8-9). ___________________________________________
What is the compound in the water layer? ________________________________
What is the product in the top organic layer? _____________________________
Calculate from the volume and concentration of NaOH previously added, at least how many mL of the 6 M HCl will be needed? Show calculations.
Write the products of the reaction (after HCl is added).________________________
11. Filter the solid using the Hirsch funnel.
What is the compound in the ethyl acetate?
Use structural formulas to complete all the questions above.
Include a detailed flow chart to show how each extraction step works in your notebook.
"Mayo": Mayo, D.W., Pike, R.M., Butcher, S.S. and Trumper, P.K. Microscale Techniques for the Organic Laboratory; Wiley: New York, 1991.
"B&F". Brown, W. H.; Christopher, S. F. Organic Chemistry, 3rd Ed., Harcourt College Publishers. San Diego, CA. 2002
Created by Evan Thompson, revised by Shane Phillips on 1/21/98 then J. Almy January, 2001. Revised by Nhu Y Stessman March 2006.
 Use a stirring rod to transfer a droplet of the water to the pH paper for this test.
 The term “to dry” an organic layer means to remove traces of water from the compounds you separate. Drying is accomplished by passing the ether solution through a pipette containing anhydrous Na2SO4 (about 2 cm of Na2SO4) into a preweighed container.
 Add the wooden splinter to the filtered solution before you put the solution on the sand bath or directly on the hot plate.