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Experiment 11 ISOLATION OF CAFFEINE FROM TEA

Experiment 11 ISOLATION OF CAFFEINE FROM TEA. Reading Assignment pp. 119 – 127 Technique 7, pp. 595 – 613 Green Lab people: download materials Technique 16, pp. 726 - 731. Caffeine. Distribution Coefficient. See page 597 for an example on how this equation is applied to extraction.

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Experiment 11 ISOLATION OF CAFFEINE FROM TEA

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  1. Experiment 11ISOLATION OF CAFFEINE FROM TEA • Reading Assignment • pp. 119 – 127 • Technique 7, pp. 595 – 613 • Green Lab people: download materials • Technique 16, pp. 726 - 731 WWU -- Chemistry

  2. Caffeine WWU -- Chemistry

  3. Distribution Coefficient WWU -- Chemistry

  4. See page 597 for an example on how this equation is applied to extraction. WWU -- Chemistry

  5. Bottom line! You will remove more solute (caffeine) from an aqueous solution by using two 1 mL portions of methylene chloride than by using one 2 mL portion of methylene chloride! See the textbook for an example. WWU -- Chemistry

  6. Separatory funnel Remove from top before you start to drain! Remember! Close stopcock before pouring stuff in the top of the funnel! WWU -- Chemistry

  7. Which layer on the top?Which layer is on the bottom? You need to know the density of the methylene chloride and the density of the aqueous phase to answer this question! WWU -- Chemistry

  8. Green extraction of caffeine from tea You will remove caffeine from tea using a Solid Phase Extraction column (SPE). Be sure to download the experiment and some of the technique materials from Charles Wandler’s web page. WWU -- Chemistry

  9. Solid Phase Extraction (SPE) SPE column filled with C-18 silica Two Neoprene adapters To house vacuum Filter flask WWU -- Chemistry

  10. C-18 silica Silica is alkylated with long chain hydrocarbon groups, using 18 carbons long. This is usually referred to as C-18 silica. WWU -- Chemistry

  11. Solid phase extraction (SPE) • The C-18 column packing is NON-POLAR • Caffeine will move more slowly because it is attracted to the column packing. • The more polar components such as tannins, gallic acid and chlorophyll move more quickly down the column with the the polar water • Once the aqueous materials have moved down the column, then you elute the caffeine with ethyl acetate. WWU -- Chemistry

  12. Sublimation Behavior WWU -- Chemistry

  13. Sublimation Apparatus To house vacuum WWU -- Chemistry

  14. Three examples: • A solid will melt if its vapor pressure is below the • applied pressure when the solid is heated to its • melting point. • 2. A solid will sublime if its vapor pressure is higher than • the applied pressure as it is heated. You will not • observe melting behavior. • If you want to sublime a solid that has a vapor • pressure of 50 mm Hg, you can do this if you reduce • the pressure, under vacuum, to below this value. WWU -- Chemistry

  15. MIDTERM EXAMINATION • Friday, February 10th • 2:00 to 2:50 PM • Distillation lab (Exp 6) is due Monday or Tuesday, depending on your section. Dr. Pavia will post answers to the questions in the post lab on his bulletin board after Tuesday so you have them for the test on Friday! WWU -- Chemistry

  16. Coverage • EXP. 2 SOLUBILITY • EXP. 3 CRYSTALLIZATION • EXP. 5 CHROMATOGRAPHY • EXP. 6 SIMPLE AND FRACTIONAL DISTILLATION AND GAS CHROMATOGRAPHY ALSO READ: • PP. 1 - 36 • 49 – 71 • 80 - 93 • TECHNIQUES 1, 2, 3, 4, 5, 6, 8, 10, 12, 14, 15 WWU -- Chemistry

  17. BRING YOUR CALCULATOR WWU -- Chemistry

  18. Experiment 52PREPARATION OF A C-4 OR C-5 ACETATE ESTER • Reading Assignment • pp. 128 – 135 • pp. 470 – 475 • Technique 3, pp. 529 – 534; 536 • Technique 6, pp. 585 – 595 • Technique 7, pp. 605 – 611 • Technique 8, pp. 617 – 629 • Technique 19, pp. 742 – 760 • Appendix 3, pp. A14 – A32 • Appendix 4, pp. A32 – A50 (probably not required WWU -- Chemistry

  19. Main Reaction WWU -- Chemistry

  20. * Ideal stopping place There may be some ROH left in the ester WWU -- Chemistry

  21. Why the extraction with NaHCO3? Ionic substance now soluble in the aqueous phase Partly soluble In the ester WWU -- Chemistry

  22. Preparation of Esters: Gas Chromatography solvent Unreacted cyclopentanol Some Alkene may Appear here WWU -- Chemistry

  23. Preparation of Esters: Gas Chromatography Ret. Time Width Peak Peak Result Time Offset Area Sep. 1/2 Status No. Name () (min) (min) (counts) Code (sec) Codes ---- ------------ ---------- ------- ------- ---------- ---- ----- ------ 1 4.2884 4.943 0.000 10754 BB 1.8 2 95.7116 6.392 0.000 240011 BB 1.4 ---- ------------ ========== ------- ======= ========== ---- ----- ------ Totals: 100.0000 0.000 250765 Total Identified Counts : 250765 counts In some cases, you may observe extra unknown peaks. Recalculate the percentages of your data based on the alcohol and ester peaks. Round off the percentages: 4.3 % cyclopentanol 95.7% cyclopentyl acetate Assume that all response factors = 1.000 WWU -- Chemistry

  24. We will not be using response factors for the esters Lab (assuming that they are 1.0). However, you may need to recalculate the data to give new areas if you have “extra” peaks that don’t belong. The example data in the previous slide can be used directly without doing calculations. The usual products include alkene from dehydration, unreacted alcohol and ester. Esters have the longest retention times, alkenes are lowest and unreacted alcohol is in the middle someplace! You will also be running the infrared spectrum of your product. WWU -- Chemistry

  25. WWU -- Chemistry

  26. Infrared spectroscopy and other material associated with the esters lab will be covered on February 17th WWU -- Chemistry

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