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Nana Mprah Lab partner-Sarah West(Data  collected) 9.29.2020, CHEM 3105-307 TA-Gary George The Extraction of 1,3,7-trimethylxanthine from Tea Leaves Purpose The purpose of this experiment is to isolate pure caffeine (1,3,7-trimethylxanthine) from a native source (tea leaves) through extraction techniques. Reaction and Physical Properties Table Compound

MW

Amount

mmol

mp

-

1.0 g

-

-

Water

154.21

10 ml

-

-

Sodium Carbonate

122.12

1.1 g

10

851

Tea

Safety Sodium Carbonate ● Risk Statements Safety Statements ○ Causes serious eye irritation Wear eye protection ○ Irritation to eyes, skin Wash skin thoroughly after Hh. handling.  Procedure 1. Open and empty a tea bag. Weigh out 1.0 g of tea leaves and staple inside the tea bag. 2. Weigh 1.1 g of anhydrous sodium carbonate and 10 mL of water and add it to a 50 mL Erlenmeyer flask. 3. Heat mixture with occasional swirling to dissolve the acid. 4. Add prepared tea bag in the flask so that it lies flat on the bottom. 5. Place a watch glass over the mouth of the flask and heat mixture to a gentle boil for 30 minutes. 6. Cool flask to room temperature 7. Transfer aqueous extract from the flask to a 12 or 15 mL to a centrifuge tube. 8. Squeeze out tea bad and set it against the side of the flask 9. Set the tea bag aside 10. Extract the aqueous solution with 2.0 mL of methylene chloride 11. Separate lower (methylene chloride) using a Pasteur pipet

12. Add a small amount of magnesium sulfate to test tube and swirl for a minute to dry 13. After a minute of drying, pipette methylene chloride into a clean, dry shell vial 14. Extract the remaining aqueous phase with four additional 2.o mL portions of methylene chloride 15. Rinse the magnesium sulfate with 2.0 mL methylene chloride and combine this wash with the earlier organic extracts 16. Carefully evaporate the solvent in the hood 17. Obtain an IR spectrum, and compare it with that of an authentic sample. Data/Observations Weight of tea leaves: 2.2537g Weight of Sodium Carbonate: 0.97g The melting point was obtained for the caffeine which was white in color and stringy in substance. Melting point documented for caffeine was between 228-234 Calculations & Results % Caffeine= (Grams of caffeine/grams of tea)x 100% %Caffeine= (0.010 g) /(2.2537 g) x 100% %Caffeine extracted= 0.444%

Conclusions/Discussion The purpose of this experiment was to extract caffeine from tea leaves. The experiment was a success, albeit the loss of some material during the extraction caused a much lower percentage of caffeine extracted. On average loose black tea had 22-28mg of caffeine per 1 gram dried matter." I expected to make around the same as 22-28mg or less of caffeine per one gram, I wasn’t very close because the small amount could be due to caffeine leftover in the tea bag when it was removed from the aqueous solution and some of it evaporating away with the extract. Also in the IR Spectra of the isolated caffeine, there are C-H bonds, but compared to the reference IR, the transmittance was low. They can’t be N-H because the wave number is a little low. Then around 1700, there are two C=O spikes similar to the ones in the reference. The purpose of this experiment was to extract caffeine from tea leaves. This extraction was successful but by no means efficient. There are significantly more efficient ways of extracting caffeine that will yield a much more pure substance. Without doing a different extraction method such as supercritical CO2, the only other way to rid the caffeine of its impurities would be to perform a recrystallization on the caffeine gathered. By doing this and forming pure caffeine crystals, the melting point would exhibit closer to what is documented that caffeine melts at, as well as seeing an accurate IR spectrum that does not include a large OH peak.

Post Lab Questions 1. Tea contains various acidic organic molecules called tannins. Given that, why is it helpful to us Na2CO3 in this experiment? It is helpful because Na2CO3 acts as a base, thus neutralizing the acidity of the carboxylic acids found in tea. Due to this neutralization, Caffeine will experience an even higher affinity with dichloromethane 2. Why does the IR spectrum of caffeine contain two carbonyl peaks? It contains two carbonyl peaks due to the fact that caffeine has two distinctly different ketones found within its structure. One carbonyl group is bonded to carbon as well as a Nitrogen. The other carbonyl group is bonded to two Nitrogen. The stretch between these bonds will occur at slightly different wavelengths. 3. 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? The reason the isolated caffeine exhibited a slightly lower melting point was due to impurities found even when performing the IR Spectrum. OH groups were found which will cause the melting point to be lower, as the caffeine is not a pure crystalline structure. In order to get the isolated caffeine to exhibit a melting point closer to the literature value, a recrystallization method could be used to isolate a pure crystal form of caffeine, free from any impurities....