Presentation on theme: "Isolation of Caffeine From “Mountain DewTM” or “Coca-ColaTM” Syrup"— Presentation transcript:
1 Isolation of Caffeine From “Mountain DewTM” or “Coca-ColaTM” Syrup Organic Chemistry Lab IFall 2009Dr. MilkevitchOct 19 & 21, 2009
2 Extraction Today: Learn a separation method Extraction: “one of the most common methods of separating an organic product from a reaction mixture, or a natural product from a plant.”We will be examining liquid-liquid extraction, attempting to separate caffeine from soft-drink syrup.
3 How Liquid-Liquid Extraction Works You have some compound in a solvent (solute)Perhaps a reaction productYou add another solvent to this solvent (which contains the solute)Solvents must be immiscibleImmiscible: incapable of mixingCommonly water and a moderately polar/nonpolar solventAn equilibrium concentrations of solute is formed between the immiscible solvents
4 Extraction, (con’t) Concentration of solute in each solvent Depends on the relative solubility of the solutein each solventThe solute will be more concentrated in the solvent in which it is more solubleResult: You can “move” a compound from one solvent to anotherFollowed by purification, characterization, etc.
5 What Extraction Is Used For To separate an organic product from water insoluble impuritiesRemember: water + moderately polar/nonpolar solvents are the most common in extractionOrganic product preferentially drawn into the organic solvent in which it is more solubleOther components drawn into or remain in waterOrganic component “freed” from water soluble impurities
6 Difference Between Extraction and Washing Extraction: removing a compound of interest from a solution or solid mixtureWashing: removing impurities from the substance of interest
7 Doing a Miniscale Extraction Pfft!!!Stopcock must be closed!Solvent + compoundVENT!!!Keep finger on the stopper!
8 After Initial Venting: Comes the Shaking!! Pfft!!Followed by venting!!!Invert multiple timesDo a minimum of 3 times!!!!!!!
9 After Shaking, Separation! 1) Place separatory funnel back inIron ring2) Let layers separate3) Drain off lower layer (methylene chloride)
10 Important Tips Concerning Extraction Always keep your finger on the glass stopper when inverting the separatory funnel!Make sure the stopcock is closed!Never discard any layer until the experiment is done!Make certain the phases are thoroughly mixed by vigorously shaking the separatory funnelVent frequently! This will prevent pressure buildup.If there is only one layer is separatory funnel and there should be two:Perhaps a wrong layer was used.Try adding a little water, and see if 2 layers formIf there is still one layer, add a little organic solventSince you didn’t discard anything, you are ok.
11 More tips If you get an emulsion: Emulsion: a yucky suspensionStir the solution with a glass rodIF all else fails, add some salt waterOR: filter through filter paper (slow and messy)OR: In this case, filter through some magnesium sulfate (will dry at the same time)
12 Drying/Breaking Emulsion Separatory funnel~ 1 cm layer of magnesiumsulfateSmall piece of cottonErlenmeyer flask
13 ProcedureMeasure out 40 ml of Coca-Cola or Mountain Dew syrup (your choice), transfer to 250 ml flaskDilute syrup with 40 ml ddH2OAdd 10 ml ammonium hydroxide40 ml of methylene chloridePour solution into a 250 ml separatory funnelMUST be supported by a ring stand + iron ringStopper funnel, and invertExtract by invert/revert separatory funnel 3X followed by ventingDo 3 cycles of thisPlace back on ring stand, Let layers separateIt may take several minutes for layers to separateYou will probably see some emulsionDrain off lower methylene chloride layer into a clean erlenmeyer flaskIf you have an emulsion:Break emulsion/ dry methylene chloride by passing the methylene chloride through magnesium sulfate lying on a cotton ball in a powder funnel (see figure)Rinse magnesium sulfate with ~ 2 ml of methylene chloride, let this drain into the erlenmeyer flaskRepeat the extractionAdd 40 ml of methylene chloride to the water layer (its remaining in the separatory funnel)
14 Procedure (con’t) Follow same extraction procedure Drain off the methylene chlorideAgain, if you get an emulsion, drain it through a fresh portion of magnesium sulfatePour your organic (i.e., methylene chloride) layers in a preweighed erlenmeyer flask (+ boiling chip)Evaporate off methylene chloride in the hoodLet coolWeight again, calculate weight of caffeine obtainedDo a TLC of your caffeineCheck it against a caffeine standard
15 Results/Conclusions Report the amount of caffeine that you obtained Conclusions: things to think aboutWas your extraction successful?Did you obtain any caffeine?What did it look like? (solid/liquid, color, etc)Any unique observations?Any problems/challenges?If so, how did you deal with them?If it wasn’t successful, then why?What did you think went wrong?How might you correct it in the future?
16 Questions to Answer1) What are 4 characteristics of a good extraction solvent?2) What is a potential problem of adding too much drying agent to a solution?3) When performing an extraction, why must the extraction solvent be immiscible with the solution that contains your reaction product?4) We use extraction almost every day in the preparation of foods & beverages. Give 3 examples of such extractions.5) Search for a method now commonly used to extract caffeine from coffee to manufacture decaffeinated coffee. Write a brief description of this method. You may search the internet or the library. Be sure to correctly reference your source(s).
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