WWU -- Chemistry Experiment 12 ISOLATION 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

WWU -- Chemistry Caffeine

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

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

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

WWU -- Chemistry 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 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 Sublimation Behavior

WWU -- Chemistry Sublimation Apparatus To house vacuum

WWU -- Chemistry Three examples: 1.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. 3.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 MIDTERM EXAMINATION Friday, May 5 th 2:00 to 2:50 PM Distillation lab (Exp 6) is due Monday so that we can grade and get it back.

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

WWU -- Chemistry BRING YOUR CALCULATOR

WWU -- Chemistry Experiment 52 PREPARATION 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 Main Reaction

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

WWU -- Chemistry Why the extraction with NaHCO 3 ? Partly soluble In the ester Ionic substance now soluble in the aqueous phase

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

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

WWU -- Chemistry 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 BB BB ========== ======= ========== Totals: Total Identified Counts : counts Assume that all response factors = 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

WWU -- Chemistry 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

Infrared spectroscopy and other material associated with the esters lab will be covered on May 12th