Lab 4- Extraction of 1, 3, 7 – trimethylxanthine from Tea Leaves PDF

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Lap Report, pretty good grade!...

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Nicole Bolling CHEM 3105-313 TA: Idris Olukoya 02/25/2021 Experiment 4: Extraction of 1, 3, 7 – trimethylxanthine from Tea Leaves

LAB REPORT 1. PURPOSE The purpose of this experiment is to successfully extract the 1, 3, 7 – trimethylxanthine from Tea Leaves by using a centrifuge tube, evaporation, and the addition of solvents. A. Compound Information: i.

Solubility of Caffeine in water:

ii.

Solubility of Caffeine in CH2Cl2 is 140mg/mL at 25 degrees Celsius:

iii.

Structure of 1, 3, 7 – trimethylxanthine:

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2. SAFETY A. Equipment: i.

Sodium carbonate (1 g)

ii.

Dichloromethane (10 mL)

iii.

Caffeinated tea leaves in bag

iv.

IR spectrometer

v.

Hot Plate

vi.

50 mL beaker

vii.

Centrifuge

viii.

50 mL Erlenmeyer Flask

ix.

Spatula

B. Tips: i.

Do not pipet CH2Cl2 over the sink.

ii.

Be careful not to heat the solid remaining in the container after the solvent has evaporated for very long because caffeine sublimes.

iii.

Carefully blow on the solution with compressed air under the hood.

iv.

Do not allow contact with skin and do not ingest.

3. PROCEDURE A. Open the tea bag and weigh the dried leaves (record mass). Pour tea leaves back into the bag and close with stapler. B. Add 15 mL of DI H2O (the two side mounted faucets with single spring-loaded handle) and 1g of sodium carbonate to a 50 mL beaker. C. Heat the beaker on a hot plate to bring the water to a boil. Cover the beaker with a watch glass to minimize water loss. D. After water begins to boil, adjust heat until the mixture is gently boiling and continue to heat for 25 minutes. E. Water may need to be added if the liquid level drops a ton. You should end up with a dark tea solution, not tea syrup. F.

Remove the beaker from the hot plate and allow the mixture to cool to room temperature.

G. Once the tea solution cools, pour half of the solution into the centrifuge tube H. Extract with 4 mL dichloromethane (CH2Cl2) by capping the tube and mixing, venting occasionally by temporarily loosening the lid. I.

Allow the layers to separate. The tube will likely need to be centrifuged for a few minutes to help separate the layers. Cap should be secured, and the tube should be balanced when centrifuging.

J.

Once the layers are clearly separated in the tube, use a pipet to remove the CH2Cl2 layer and transfer it to a small container such as your 50mL Erlenmeyer flask. All CH2Cl2 used in the following extraction steps will be added to this flask. Do not pipet CH2Cl2 over the sink.

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K. Repeat the extraction of the aqueous solution still in your centrifuge tube with another 4 mL of CH2Cl2 and combine the CH2Cl2 layer with the solution in your flask with the other CH2Cl2 solution. L. Transfer the aqueous solution from your tube to a different container and keep until you no longer need it. M. Pour the other half of the concentrated tea solution from your 50 mL beaker into the centrifuge tube. Use a spatula to squish the extra liquid from the tea in the tea bag. N. Extract this portion of the concentrated tea solution with two portions of 4 mL of CH2Cl2 following the same procedure that you used above with the first half of the solution. O. Add the CH2Cl2 layers to the same flask containing the other CH2Cl2 extractions. P.

Dry the combined organic layers using anhydrous MgSO4. Remember this is done by adding small amounts of MgSO4 and swirling the solution.

Q. Keep adding small amounts with swirling until some of the added solid does not clump and remains free flowing. (Should look like a snow globe when swirled). Solution is dry and can be decanted/filtered into a clean dry container for solvent evaporation. R. Clean and dry 50 mL beaker and use it as the container for evaporating the solvent from dry CH2Cl2 caffeine solution. S. Get mass of isolated caffeine from tea leaves. T.

Solvent evaporation is done in the hood. Blow compressed air on the solution to evaporate it while heating the solution on a hot plate. Don’t heat the solid after the solvent has evaporated.

U. Note the color and consistency of extracted caffeine. V. Obtain melting point of the solid. W. Caffeine melts at 238 degrees Celsius and sublimes at 178 degrees Celsius. Include the percent of caffeine isolated from the source of tea by mass in your calculation section.

4. DATA/ OBSERVATIONS: A. The data taken observed the percent transmittance compared to the wavenumbers (cm-1). The color of the extracted caffeine was dark, but I cannot determine the consistency with the picture. The percent of caffeine isolated from the source of tea by mass was approximately 1.4 % according to my calculations from the provided experiment notes.

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5. RESULTS: A. Throughout the course of the experiment, the use of a centrifuge tube, evaporations, and the addition of solvents extracted the 1, 3, 7 – trimethylxanthine from Tea Leaves. Additionally, the melting point range of the solid was 215.5-229.8 degrees Celsius. This could’ve been skewed due to the fast rate at which the person was going since caffeine normally melts at 238 degrees Celsius.

6. POST LAB QUESTIONS: A. Tea contains various acidic organic molecules called tannins. Given that, why is it helpful to use Na2CO3 in this experiment? i.

It is helpful to add Na2CO3 because it ensures that the acidic components in the tea leaves remain water soluble and that caffeine is the free base.

B. Why does the IR spectrum of caffeine contain two carbonyl peaks? i.

The IR spectrum of caffeine contains two carbonyl peaks because caffeine contains two carbonyl groups.

C. Why might the melting point of your isolated caffeine be lower than the literature value? What procedure involving your isolated caffeine sample might be used (other than sublimation) to get caffeine that exhibits a melting point closer to the literature value? i.

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The melting point of the isolated caffeine may be lower than the literature value because the product may not be pure. In order to get caffeine that exhibits a melting point closer to the literature value (238 degrees Celsius), chlorophyll and other water-soluble components should still be in the caffeine despite the addition of more heat while extracting the caffeine from the solution....