EXPT 3 extraction

By first mixing the phensuprin with dichloromethane

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Unformatted text preview: loromethane, the sucrose can be removed by simple filtration. This is an example of a separation based on solubility. Next, the dichloromethane is extracted with sodium bicarbonate solution. The acetylsalicylic acid, as the name implies, is an acid and sodium bicarbonate is a base. They react, as shown below, to give a salt which is now more soluble in water than dichloromethane. The acetanilide is not affected by treatment with a weak base like sodium bicarbonate, so the third component remains dissolved in the dichloromethane. Since water and dichloromethane are not miscible, the layers can be separated, thus separating the two analgesic components. The acetylsalicylic acid can then be recovered by converting the salt back to the acid with concentrated hydrochloric acid. O O OH O O NaHCO3 CH3 O-Na+ O O HCl O CH3 H2CO3 + OH O O H2CO3 + NaCl CH3 H2O + CO2 The technique sections which are applicable to this experiment (filtration, fluted filter paper, drying agents, solvent-solvent extraction using acid/base chemistry, melting points and evaporation) are in files under Techniques and must be read and understood before beginning the experiment. Procedure: CHEMICAL HAZARDS: Acetylsalicylic acid: POISON, IRRITANT Acetanilide: TOXIC, IRRITANT Dichloromethane: CARCINOGEN, TOXIC, IRRITANT Hydrochloric Acid: POISON, TOXIC BY INHALATION, CORROSIVE IRRITANT Accurately weigh approximately 2 g of the Phensuprin sample into a 125 ml Erlenmeyer flask. Add 50 ml of dichloromethane and vigorously stir the mixture until no more solid appears to dissolve. Make sure that any clumps of solid are broken up during the stirring. Weigh and flute a piece of filter paper. Filter the mixture through the preweighed filter paper by gravity filtration. Wash the collected solid (the sucrose) with 5 ml of dichloromethane. Place the filter paper containing the collected sucrose in a beaker to dry until the next week. When the filter paper and sucrose are completely dry, weigh the filter paper plus solid, and calculate the amount of sucrose recovered. Report the result as a weight and percent of the total weight o...
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