3 - Caffeine Extraction Worksheet

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University of California, Los Angeles *

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14CL

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Chemistry

Date

Jan 9, 2024

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pdf

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4

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Caffeine Extraction e [Extraction:; o Selective 1solation of a specific compound from a solution containing a mixture of substances o Liguid-liquid extraction: the solute i1s extracted from one solvent to another because it’s more soluble in the second solvent e (affeine [ ab: o Requirements: m #1. Two Immiscible solvents - they do not mix m #2. The solvents must form two separate phases or layers m HOW do you isolate substance? You shake them together! - this will make compound go into your organic solvent o Things Used: m Ethyl Acetate: the second (organic) solvent m NaCl: inc. polarity of water to make caffeine move to ethyl acetate m Drying Agent (Na2SO4): will dry out any H20 that was left Steps: 1. Add NaCl to salt out a. Basic principle: Like dissolves like
i. This means that polar compounds dissolve in polar solvents ii. Non-polar compounds dissolve in non-polar solvents b. SALTING OUT: increasing the polarity of the aq solution in order to dec the solubility of compound in aq liquid and inc the solubility of compound in organic liquid. 2. Extract the caffeine into ethyl acetate and combine the organic layers 3. Add Anhydrous Sodium Sulfate to dry the water still left inside 4. Filter out anhydrous sodium sulfate and evaporate ethyl acetate. = PO 7dd anh Advis AU G ot akor - (NQL&)w) s Avy 19 agent cokf = L’M’LSO Y J =
Practice Problems: Equations: e For partition coefficient: o K=(CHCy) o K=(C)/C) o K = (solubility of S in solvent 1)/(solubility of S in solvent 2) e For the amount of compound remaining in the aqueous solution: o W =W, (V,/(K*V)+V,)" 1. Organic compound X will be placed in an organic + aqueous solution. Organic solvent A has a solubility of 270 g/mL and aqueous solvent A has a solubility of 9 g/mL. Organic solvent B has a solubility of 150 and aqueous solvent B has a solubility of 3 g/mL. Which combination of organic + aqueous solvents would result in less extractions needed? a. A:C,/C,=@270¢g/mL)/ (9 g/mL) =30 b. B:C,/C,=(150 g/mL) /(3 g/mL) =50 c. Group B would result in less extractions needed because if the ratio is bigger, then the solute dissolves better in the organic layer. 2. Solute A has a distribution (partition) coefficient of 3 between water and ether. 280 mg of solute A was dissolved in 15mL of water. If this solution is extracted 3 times with 10mL of ether, how much of solute A will be in the combined organic phase? In the aqueous phase?
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a. W;=W,(V,/(K*V)+V,) =280mg (15mL / (3*10mL) + 15mL)’ b. W, =10 mg left in aqueous (water) after 3 extractions c. 270 mg left in organic (ether) after 3 extractions 3. There is 175 mg of solute left in the aqueous layer after 2 extractions with water and propanol. The solute was dissolved with 20 mL of water and 25 mL of propanol.The partition coefficient was 2.3 What was the original amount of solute in grams? a. 175 mg=W,(20mL /(2.3*25mL) + 20mL)* . W,;=2627.7Tmg=26g