Presentation on theme: "Organic Chemistry Lab 315 Fall, 2014 Note that the reading for this experiment is Technique 12. The experiment (Extraction of Caffeine) is in the Manual."— Presentation transcript:
Organic Chemistry Lab 315 Fall, 2014 Note that the reading for this experiment is Technique 12. The experiment (Extraction of Caffeine) is in the Manual.
DUE DATES Today –At beginning of lab – Identification of an Unknown Report –Problem #1, Part II, Spectroscopy Problem Set –At end of lab -- copy of laboratory notebook pages for today's experiment (do not turn in your pre-lab notes or in-class notes) Next Week –Part II, #2 Spectroscopy Problem Set –Extraction of Caffeine Report
Report Notes – Last Week Pay attention to significant figures in calculations. Properly labeled vial example in Pavia (page number was written on the blackboard). It must include the melting point range – you always report ranges (and it is an indication of purity).
In Lab Today Learn the new technique of extraction Drying organic solvents (See p. 697 in Pavia)
Experiment Notes Beaker containing dissolved caffeine and insoluble binder Funnel with glass wool as filter Separatory funnel supported on iron ring on ring stand Stopcock closed Beaker underneath “just in case”
Experiment Notes Beaker containing dissolved caffeine and insoluble binder Funnel with glass wool as filter Separatory funnel supported on iron ring on ring stand Stopcock closed Beaker underneath “just in case” Separatory funnel with stopper Aqueous layer on top Methylene chloride layer on bottom (contains caffeine) Drain off CH 2 Cl 2 bottom layer into beaker Total 3 extractions (8 ml x 3)
Experiment Notes Extractions in a Separatory funnel Add liquids using a glass funnel in order to not contaminate the neck of the sep. funnel. After replacing the stopper, turn the sep. funnel upside down to vent. Repeat if audible gas escapes. Shake/swirl gently, but thoroughly, to mix the immiscible liquid phases. Emulsion may form in this experiment. Caffeine is in the bottom CH 2 Cl 2 layer. Drain bottom layer through stopcock into 100 ml beaker. [This is one extraction.] Add additional CH 2 Cl 2 (using glass funnel) from top. Extract with CH 2 Cl 2 three times total, combining all extracts in beaker.
Experiment Notes There will be water dissolved in the CH 2 Cl 2 extracts that needs to be removed. Organic solvents are “dried” by using an anhydrous salt that can absorb the water and become hydrated. See Section 12.9 in Pavia for common drying agents and equations for anhydrous salt → hydrated salt MgSO 4 + H 2 O → MgSO 4 ∙10H 2 O When you are ready to dry your solution, bring it to the instructor’s bench. After drying, decant the solution into a pre-weighed beaker.
Experiment Notes Make sure the balance is displaying ±.001g Evaporate solvent using a hot plate UNDER THE HOOD. Do not recrystallize caffeine. Weigh the beaker and mostly dry caffeine. Place your caffeine in a properly labeled vial. See Pavia for an example of a correctly labeled vial. Caffeine tablet contains 200 mg of caffeine. The remainder is “inert ingredients”. Calculate the % isolation based on the mg caffeine in the 2 tablets.
Report for Next Week Report Form in Manual Separation scheme (flow chart of procedure for separating a pure product from reaction by- products or mixture impurities) –See explanation and example in Manual/class web page There is no written report required (major grading will be for the Separation Scheme – be sure you understand it)
Report for Next Week Some additives in Vivarin: –polyethylene glycol and polysorbate 80 (water-soluble) –titanium dioxide and silicon dioxide (water- insoluble) –D&C yellow #10 and yellow #6 aluminum lake (water-insoluble) –carnauba wax (water-insoluble)
Report for Next Week These additives should be included in your Separation Scheme for isolating caffeine from Vivarin tablets. You do not need to find the structures for these compounds. You can ignore the effect of Na 2 CO 3 on the water-solubility of any of these additives, although it should be included in the scheme. (Na 2 CO 3 was added to the Vivarin-water solution.)
Report for Next Week Your Separation Scheme should resemble the one done for isolation of caffeine from tea leaves, shown in class. Tea leaves separation Right-click on the hyperlink above, and then choose “open hyperlink”’