Experiment 12 ISOLATION OF CAFFEINE FROM TEA OR COFFEE

1. Experiment 12ISOLATION OF CAFFEINE FROM TEA OR COFFEE • Reading Assignment • pp. 87 – 99 • Technique 12, pp. 669 – 693 • Green Lab: Not available spring 06 • Technique 17, pp. 745 - 749 WWU -- Chemistry

2. Caffeine WWU -- Chemistry

3. Distribution Coefficient See page 670-671 for an examples on how this equation is applied to extraction. WWU -- Chemistry

4. 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

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

6. 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

7. Green extraction of caffeine from tea- not an option spring 06 You will remove caffeine from tea using a Solid Phase Extraction column (SPE). Experiment not available spring quarter 2006 WWU -- Chemistry

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

9. 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

10. 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

11. Sublimation Behavior WWU -- Chemistry

12. Sublimation Apparatus To house vacuum WWU -- Chemistry

13. 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

14. MIDTERM EXAMINATION • Friday, May 5th • 2:00 to 2:50 PM • Distillation lab (Exp 6) is due Monday so that we can grade and get it back. WWU -- Chemistry

15. Midterm Coverage • Experiments • EXP. 2 Solubility • EXP. 3 Crystallization • EXP. 5 Chromatography • EXP. 6 Simple and Fractional Distillation Gas Chromatography • Also Review Techniques: • Techniques 5, 6, 8, 9, 10, 11, 13, 14, 15, • 19, 20, 22 WWU -- Chemistry

16. BRING YOUR CALCULATOR WWU -- Chemistry

17. Experiment 52PREPARATION OF A C-4 OR C-5 ACETATE ESTER • Reading Assignment • Experiment 56, pp. 498 – 501 • Experiment 13, pp. 103 – 108 • Essay on esters, 99 – 102 • Technique 12, pp. 677 – 688 • Technique 13, pp. 694 – 702 • Technique 14, pp. 703 – 732 • Technique 25, pp. 833 – 867 WWU -- Chemistry

18. Main Reaction WWU -- Chemistry

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

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

21. Drying agents • NaCl functions as a preliminary drying step. It also helps to break emulsions. • Anhydrous sodium sulfate removes remaining water: 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 May 12th WWU -- Chemistry