Spring 2017 Renan Gongora Week Two: Extraction
Disclaimer The information provided here is to help facilitate learning and a smoother in-lab experience but you need to read all procedures!!! Furthermore, these are not complete procedures and all of the procedure (unless modified should be followed per the lab manual, the Pavia text, found on the appropriate pages indicated in the syllabus)
Extraction: Motivation atural products (organic chemicals that exist in nature) can be extracted from either plants or animals caffeine Common examples caffeine vanillin H vanillin
Extraction: Technique Experiment Background Theory You will have to use this for your lab reports (consequent preparative) You will need it for the quizzes Procedures Part A Part B Part D H H
Extraction: Technique (Theory) Types liquid-liquid (separatory funnel) solid-liquid (Soxhlet Extractor) Uses Isolation/Purification Reaction Setup Implemented Two immiscible solvents Solvents separate by density Where is the compound? Miscible means solvents are able to mix freely Immiscible liquids form separate layers because they do not mix in any proportion Denser liquid will be found at the bottom Solute will be found in the solvent that better dissolves it
Extraction: Background Theory The glassware/setup used here (separatoryfunnel) How to safely setup How to shake How to dispense liquid Combatting Emulsions How density relates to extraction Drying the wet organic layer Removal of the drying agent (inorganic salt) Separatory funnel
Extraction: Separatory Funnel How to separate a mixture of compounds?
Extraction: Separatory Funnel When draining: When shaking: Point away from others! Vent frequently (windmill technique)
Extraction: Separatory Funnel Where is the dense layer? Top or bottom?
Extraction: Combatting Emulsions What is an emulsion? (ask students what it is and why are they bad for separation, don t give answer let them think about it) In general, how to get rid of them: 1. Gently swirl not to be confused with shaking 2. Add sodium chloride 3. Transfer to a centrifuge tube and centrifuge 4. Wait forever Follow procedure but these are common ways to overcome emulsions
Extraction: Relative Densities of Common Solvents
Extraction: Technique Experiment Background Theory They will have to use this for their lab reports for the preparative experiments They will also need it for the quizzes They will also need to refer to this prior to reading the preparative experiments Procedures Part A Part B Part D H
Extraction: Procedure A Goal: extract caffeine from an aqueous solution using methylene chloride or dichloromethane (DCM) *done in the fume hood Step 1 (preparation): Add exactly 0.170g of caffeine and 10 ml of water to a centrifuge tube and shake Step 2 (extraction): transfer the solution to a separatory funnel H Students should have already finished the prelab calculation for each wash. This will let you know how much caffeine is theoretically remaining in the aqueous layer after each wash.
Extraction: Procedure A *done in the fume hood Step 3: Add 5 ml of DCM and stir upright without stopper Step 4: Then cap and gently shake one time (with cap on). Caution: pressure will buildup quickly because DCM is very volatile. Let layers settle and separate Step 5: Remove the organic layer (What is the density of DCM?, what layer should you remove?)
Extraction: Procedure A Step 6: repeat the process two more times (on the aqueous layer!!) to extract the remaining caffeine Step 7: Combine all wet organic layers and dry with sodium sulfate. Wait until organic layer is dry (you need to know how to identify when it is dry). Step 8: With a Pasteur pipette, remove the organic solution from the inorganic drying agent (without getting any of the solid) and transfer to a clean (PREWEIGHED) Erlenmeyer flask
Extraction: Procedure A Step 9: Evaporate the remaining solvent leaving only the caffeine (white solid) Evaporating excess solvent BEWARE: SLWLY TUR THE AIR VALVE. They are very tight and very sensitive. This means you can spray the entire contents of your work all over the hood (or even worse someone else) Turn on air and then place over flask. ot the other way around.
Extraction: Procedure A Weigh the flask once solvent has been removed and record the weight of the caffeine isolated by the difference of the flask after solvent evaporation minus the flask weight
Extraction: Procedure A (What to Report?) 1. Show calculations for the amount of caffeine that should extracted by the three 5.0 ml portions of DCM (include in notebook!) 2. Report the amount of caffeine isolated. Compare the weight with the amount of caffeine calculated in the prelab calculation
Extraction: Technique Experiment Background Theory They will have to use this for their lab reports for the preparative experiments They will also need it for the quizzes They will also need to refer to this prior to reading the preparative experiments Procedures Part A Part B Part D H
Extraction: Procedure B Modification: o succinic acid in this lab! Goal: Separately, determine the weight of benzoic acid and sodium benzoate in the organic layer Experimentally, determine the distribution coefficient for each compound benzoic acid and sodium benzoate Question: They are structurally similar but will they have the same distribution coefficient and the same affinity for the organic solvent DCM? This will let you know how much compound is theoretically remaining in the aqueous layer after each wash. a+ - H
Extraction: Procedure B *done in the fume hood Step 1: Place 0.1 g of one of the solids (benzoic acid R sodium benzoate) into a centrifuge tube Step 2: Add 4 ml of DCM followed by 4 ml of water to this tube and shake Step 3: After layers settle, remove the organic layer
Extraction: Procedure B Step 4: repeat the process two more times (on the aqueous layer!!) to extract the remaining benzoic acid or sodium benzoate Step 5: Combine all wet organic layers and dry with sodium sulfate. Wait until organic layer is dry (you need to know how to identify when it is dry). Step 6: With a Pasteur pipette, remove the organic solution from the inorganic drying agent (without getting any of the solid) and transfer to a clean (PREWEIGHED) Erlenmeyer flask
Extraction: Procedure B (What to Report?) 1. Report in a table form the distribution coefficients for the two solids: benzoic acid and sodium benzoate (in notebook) 2. Is there a correlation between the values of the distribution coefficients and the polarities of the two compounds? Explain (in notebook)
Extraction: Technique Experiment Background Theory They will have to use this for their lab reports for the preparative experiments They will also need it for the quizzes They will also need to refer to this prior to reading the preparative experiments Procedures Part A Part B Part D
Extraction: Procedure D Modification(s): Do not obtain melting point Goal: Removal of acid and/or base impurities from an impure compound Question: How to only remove these impurities and purify the compound? Experimentally, determine the distribution coefficient for each compound benzoic acid and sodium benzoate This will let you know how much compound is theoretically remaining in the aqueous layer after each wash. impure impure
Extraction: Procedure D
Extraction: Procedure D *done in the fume hood Step 1: Place 0.36 g of one of the solids (fluorene or fluorenone) into a test tube Step 2: Add 10 ml of ether (diethyl ether) to this tube and shake Step 3: Transfer this solution to a separatory funnel Step 4: Add 5 ml of 1M ah After layers settle, remove the organic layer Step 5: repeat this process in Step 4 twice with the organic layer and follow the rest of the procedure (acid wash and sodium chloride wash, drying and removal of solvent) You are here Going here
Extraction: Procedure D Step 4: repeat the process two more times (on the aqueous layer!!) to extract the remaining benzoic acid or sodium benzoate Step 5: Combine all wet organic layers and dry with sodium sulfate. Wait until organic layer is dry (you need to know how to identify when it is dry). Step 6: With a Pasteur pipette, remove the organic solution from the inorganic drying agent (without getting any of the solid) and transfer to a clean (PREWEIGHED) Erlenmeyer flask
Extraction: Procedure D (What to Report?) 1. Answer the following questions about the first and the second ah extracts. 1. Comment on the amount of precipitate for both extracts when HCl is added. 2. What is the precipitate formed when HCl is added? 3. Does the amount of precipitate in each tube indicate that all the acids impurity has been removed from the ether layer containing the unknown neutral compound?
Extraction: Summary Background Theory They will have to use this for their lab reports for the preparative experiments They will also need it for the quizzes They will also need to refer to this prior to reading the preparative experiments Procedures Part A Part B Part D H H