CHEM 3112 Lecture 3: Extraction

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10 Feb 2017

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Separation of a substance from one phase by another. Often a step in isolating a product of an organic reaction. Removal of a desired compound from a solid or liquid mixture by a solvent. Organic compounds separated from aqueous by immiscible organic solvent. Aqueous mixture to be extracted is added to separatory funnel. Mixture is shaken then allowed to separate into layers. Organic layer is dried using drying agent, filtered and evaporated. Place small amount of solvent in separatory funnel. Cap and invert while holding stopper in place. If it leaks exchange with the store room. Always have flask below prior to adding anything in sep funnel. Make sure stopcock is tight, gently twist nut until secure. If solutions are immiscible will see two layers, here water is yellow and dcm is clear. Hold stopper in place and turn on its side to carefully shake the contents. Stand up and return to ring stand allowing layers to settle.

Related Questions

You have dissolved 2 g of a mixture of benzoic acid and naphthalene in 30 ml of diethyl ether and started the extraction procedure.

Match the question with an appropriate answer from the drop-box. Before answering the questions below get the data about density of the solvents you use.

You transferred the solution of benzoic acid and naphthalene in diethyl ether to the separatory funnel and added on top15 ml of 2.5 M NaOH solution. Where you would find the aqueous solution, at the top or at the bottom of the separatory funnel?

You transferred prepared solution of benzoic acid and naphthalene in diethyl ether to the separatory funnel and added on top15 ml of 2.5 M NaOH solution and you shook the separatory funnel. Where you would find the aqueous solution, at the top or at the bottom of the separatory funnel?

After completing the extraction the procedure in the textbook recommends you to transfer the organic solution into a clean Erlenmeyer flask. What is the composition of organic solution?

After completing the extraction the procedure in the textbook recommends you to transfer the aqueous layer into a clean Erlenmeyer flask. What is the composition of aqueous layer?

Possible answers for all above questions:

1.The aqueous layer is a solution of benzoic acid in water

2. The organic solution is a solution of sodium benxoate in 2.5M aqueous solution

3. The aqueous layer is a solution of sodium benzoate and excess of sodium hydroxide in water

4. Aqueous solution will be found at the bottom of the separatory funnel

5. The organic solution is a solution of aphthalene in diethyl ether

6.The aqueous layer is a solution of sodium benzoate in water

7.The organic solution is a solution of benzoic acid in diethyl ether

8. The organic solution is a solution of naphthalene an benzoic acid in diethyl ether

I need to know the procedures of the experiment below :

Separation of a Three-Component Mixture by Extraction â

benzoic acid ethyl 4-hydroxybenzoate diphenyl sulfone

A 1.5-gram sample of a 1:1:1 (by weight) mixture of benzoic acid, ethyl 4-hydroxybenzoate and diphenyl sulfone was added to a 125 mL separatory funnel. Isopropyl acetate (20 mL) was added to the separatory funnel and the mixture swirled until all solids had dissolved. The solution was sequentially extracted with saturated aqueous NaHCO3 solution (4 X 5 mL), then with water (1 X 5 mL); with the aqueous extracts from each extraction being added to a 50 mL beaker (beaker 1). [The separatory funnel should be shaken for at least 1 minute during each of the four NaHCO3 extractions. Venting of the funnel should be done every 20-25 seconds during each extraction. When draining off the aqueous layer in these and all subsequent extractions leave a two mm tall layer of aqueous solution in the separatory funnel. This greatly reduces the amount of organic layer that contaminates the aqueous extracts.] Next the organic layer was extracted sequentially with 5% aqueous NaOH solution (3 X 5 mL) then with water (1 X 5 mL). Each aqueous extract was collected in a 50 mL beaker (beaker 2). [The separatory funnel should be shaken for at least 1.0 minute during each NaOH extraction..] The remaining organic layer is extracted with saturated aqueous NaCl solution (5 mL) and the aqueous layer is discarded [Do not leave any water in the funnel after this extraction]. The organic layer is transferred to a 50 mL erlenmeyer flask (flask 3). The separatory funnel is washed with isopropyl acetate (2 X 2 mL) with each washing being added to flask 3. The organic solution in flask 3 is dried (Na2SO4) then decanted into a tared 50 mL Erlenmeyer flask (flask 4). The drying agent is washed with isopropyl acetate (2 X 1 mL) with each rinse being added to flask 4. The solvent in flask 4 is evaporated to give crude diphenyl sulfone as a white solid: .416 g, 83.2%, M. pt.=121-127oC. [Evaporate the solvent using a hot plate sat on a moderate (4) setting. You must be very careful not to overheat the product when all the solvent has boiled away. The only way to actually know when all of the solvent has been removed is to weight the flask at the point of â presumed drynessâ, then reheat for a few seconds and re-weigh the flask. If the weight does not change, the product is solvent free. An alternative, and probably better, procedure is to evaporate the isopropyl acetate until only 3-5 mL of solution remains, cool, add hexane (10 mL), chill in an ice bath then filter. Both procedures work well. If insufficient time remains to isolate this material on day 1, then store the dried isopropyl acetate solution in your drawer until the next lab period. The solvent will have evaporated by then. Optional: tlc (alumina,

70/30 hexane/ethyl acetate) showed a single spot, Rf = .58. The crude product is recrystallized from toluene to give the crude product; M. pt.= 125-127ï° C.]

The aqueous solution in beaker 1 was acidified (acid to litmus paper) by the addition of 6 M HCl solution to give a white precipitate. [Caution! Foaming will occur due to liberation of CO2] After cooling the resulting mixture in an ice bath for 10 minutes, the solid was isolated by vacuum filtration, washed with ice water (3 X 1ml), and air dried to give crude benzoic acid as a white solid: .358 g, 71.6%, M. pt.= 115-120oC. [OPTIONAL: tlc (alumina, 70/30 hexane/ethyl acetate) showed a single spot (Rf = .03). This material was recrystallized from water to give pure benzoic acid; M. pt. = 118- 120ï°C.]

The aqueous solution in beaker 2 was acidified (acid to litmus paper) by the addition of 6 M HCl to give a white precipitate. The resulting aqueous mixture was cooled in an ice bath for 10 minutes. The resulting white solid was isolated by vacuum filtration, washed with ice water (3 X 1 mL), and air dried to give the crude ethyl 4-hydroxybenzoae: .353 g, 70.6%, M.pt.= 113-117oC. [Optional: tlc (alumina, 70/30 hexane/ethyl acetate) showed a single spot (Rf = .42). The crude material was recrystallized from 1/1 toluene/hexane to give the pure ethyl 4-hydroxybenzoate as a white solid; M. pt.= 115- 117ï°C.]

CHEM 3112 Lecture 3: Extraction

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