Experiement No 3

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Chemistry

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Jan 9, 2024

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Experiment No. 3 – Acid/Base Extraction University of South Carolina CHEM 331L – 018 TA October 3, 2023

Purpose The purpose of this lab is to be able to extract different compounds from one solution by creating multiple reactions by manipulating acids and bases. Objectives The objective of this lab is to perform simple extractions of acids/bases to separate a strong and a weak organic acid, along with a neutral compound. In addition, each component will be recrystallized and melting points will be recovered. After recrystallization, percent recovery will be calculated of the entire mixture, along with the composition of each component. Introduction When compounds are dissolved in a media, extraction is used to isolate the compound(s) based on solubility (Atim 2020). To extract, there are 3 types: solid/liquid, liquid/liquid, and acid/base (Atim 2020). For a solid/liquid extraction, the solid solute is separated by dissolving it in a liquid phase leaving three items: insoluble solids, solvent, and the now liquid solute (Atim 2020). In this case, just the soluble part of the solid was extracted (Atim 2020). For example, when making coffee, you extract the soluble compound from the coffee beans leaving coffee (liquid solute and solvent) and the coffee beans (insoluble solid). For a liquid/liquid extraction, a compound is pulled from liquid to another (of which are not mixable) (Atim 2020). This is done so by separation based on density and polarity (Atim 2020). For acid/base extractions (extraction method being conducted in this experiment), a series of acid/base reactions are conducted to separate strong and weak acids, along with neutral and based organic compounds/substances (Atim 2020). Liquid/liquid and acid/base extractions are the most common in organic instances to separate product (Atim 2020). Since an acid/base extraction will be conducted, acids will need to be neutralized (Atim 2020). To do this, sodium bicarbonate will be used to react with a strong

acid to create a salt (Atim 2020). To neutralize the strong acid, sodium hydroxide will be added to form an ionic compound (Atim 2020). For these extractions, pressure will buildup due to solvent vapors from the exothermic reaction(s) (Atim 2020). To alleviate this pressure, the separatory funnel must be vented frequently (Atim 2020). Both of which will be dissolved into the aqueous layer and will be removed to only leave a neutral compound (Atim 2020). A good solvent in an extraction would be a good solvent for recrystallization (Atim 2020). It will have a low boiling point, low reactabiliy (with the solute/other solvents), not flammable/toxic, inexpensive, and immiscible with water (Atim 2020). An immiscible solvent is necessary because when doing extractions, compounds are being separated and need to stay separate (Atim 2020). If they mix, then they won’t be able to be extracted easily (Atim 2020). During this separation, emulsions have the chance of forming (Atim 2020). An emulsion is the suspension of one liquid in another (Atim 2020). During extraction, emulsions want to be avoided because it won’t result in a clean-cut separation and will make extracting the full volume of the compound difficult (Atim 2020). To avoid emulsions, the solution will be left alone until two layers have formed and the aqueous layer that is formed will be made very ionic to create another buffer (Atim 2020). Once the extraction has completed, further purification must be done to ensure that the solution is just solute and solvent (Atim 2020). Organic solvents tend to dissolve traces of water in addition to the compound; therefore, by drying the organic layer (adding drying agents to remove the water from the solvent), the compound can be isolated in the solvent (Atim 2020). Reaction Schemes

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Separatory Funnel: 1 mixture of 3 compounds Separatory Funnel: mixture of 2 compounds Separatory Funnel: only 1 compound Test Tube B Test Tube C Reagents/Structures

Name, Structure, MW ( g / mol ) Meltin g ° C Boilin g ° C Densit y g / mL Properties Safety Diethyl Ether C 4 H 10 O 74.12 -116.3 34.6 .7134 Colorless liquid with a characteristic, sweet, ether odor Moderately toxic to humans by ingestion; absorbs through skin; FLAMMABLE Hydrochloric Acid HCl 36.46 -30 >100 1.2 Corrosive material It is a highly corrosive irritant of the skin, eyes and mucous membranes; CORROSIVE Magnesium Sulfate MgSO 4 120.36 1124 -- 2.66 HYGROSCOPIC ; Drying agent; White powder Desiccant Sodium Hydroxide NaOH 39.99 318 1390 2.13 Corrosive material; Colorless, odorless solid; HYGROSCOPIC It is a highly corrosive irritant of the skin, eyes and mucous membranes; CORROSIVE Benzoic Acid C 7 H 6 O 2 122.12 122.4 249 1.32 Flavoring preservative; White powder Mild irritant to skin, eyes, and mucous membranes; toxic by skin absorption; when heated to decompositi on, it emits acrid smoke and irritating fumes

2-Naphthol C 10 H 8 O 144.17 122 286 - White to brown powder; LIGHT SENSITIVE TOXIC 1,4- dimethoxybenzene C 8 H 10 O 2 138.16 54-56 212.6 1.035 White solid Causes somnolence and depressed activity. sodium bicarbonate NaHCO 3 84.00 50 1413 5.165 White crystals When heated to decompositi on, this compound emits toxic fumes of carbon monoxide, carbon dioxide and sodium oxides Procedure 1. Set up ice bath in 400mL beaker. 2. Label 4 large test tubes from A-D respectively. 3. Weigh test tube D and record weight. 4. Obtain 1g of ternary mixture and add to test tube A. Dissolve in 6mL of diethyl ether. 5. Move solution to separatory funnel. 6. Add 2.0mL of 10% NaHCO 3 into separatory funnel. 7. Swirl two layers gently and ventilate frequently to avoid pressure build up. 8. Remove lower aqueous layer in test tube B.

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a. There should now only be the ether layer that contains the weak acid and neutral compound. 9. Place test tube B in ice bath. 10. Add small amount of solvent (diethyl ether) to separatory funnel if necessary. 11. Add 2.0mL of NaOH. 12. Repeat step 7. 13. Remove lower aqueous layer in test tube C. 14. Place test tube C in ice bath. 15. Add 1.4mL of deionized water into separatory funnel. 16. Shake and drain the now separated aqueous layer. a. This was done to remove any leftover inorganic material. 17. Place remaining ether layer into test tube A, which should now only contain the neutral 1,4-dimethoxybenzene. 18. Add small amount of MgSO 4 to test tube A and allow ether layer to stand for 5 minutes. 19. Filter using gravity filtration and pour ether layer in test tube D. 20. Evaporate ether layer. 21. Record melting point and calculate percent composition. 22. Add small amount of solvent (diethyl ether) to separatory funnel if necessary. Test Tube B: Aqueous solution of sodium benzoate 1. Add 1.4mL ether to test tube B to remove impurities. 2. Add 3M HCL slowly with drops until precipitate forms. 3. Place tube B in ice bath and complete crystallization.

4. Collect crystals via vacuum filtration, dry, and measure melting point and calculate percent composition. Test Tube C: Aqueous solution of sodium 2-Naphthoate 1. Add 1.4mL ether to test tube C to remove impurities. 2. Add 3M HCL slowly with drops until precipitate forms. 3. Place tube C in ice bath and complete crystallization. 4. Collect crystals via vacuum filtration, dry, and measure melting point and calculate percent composition. Waste Reagent Disposal After experiment is complete, dispose of all organic solids into the solid organic waste container. Dispose of ether in organic liquid waste container. Dispose of soiled gloves, paper towels, and broken glass in appropriate containers (Atim 2020). References/Resources Atim, S., Chemistry 331L/333L Laboratory Manual Essentials of Organic Chemistry Laboratory . QDE Press Inc. Montgomery, Al, 2020. p. 35-51.