Extraction of Caffeine from Tea

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Experiment 1: Extraction of Caffeine from Tea The primary objective of the experiment is to separate the caffeine from tea leaves. The mixture of tea and the calcium carbonate is separated from tea leaves by vacuum filtration. The solvent used in extraction of caffeine is dichloromethane. Anhydrous magnesium sulfate is added to the dichloromethane solution to dehydrate the mixture. The dichloromethane is then separated from the mixture in the rotary evaporator. Figure 1: The structure of caffeine is very similar to those of purine bases (adenine and guanine) in DNA, therefore caffeine is a good substance to practice on for dealing with nucleic acids. Procedure Approximately 10g of tealeaves, CaCO3 (4.8g, 0.048 mol) and deionised H2O (100mL) is added into a beaker and boiled for 15 minutes. The mixture is then cooled to 20˚C and is filtrated using a Buchner funnel (vacuum filtration). The extraction process is when a solvent, dichloromethane (15mL) is added to the filtrate in a separatory funnel; the mixture is gently swirled together 3 times, and stopcock is released in between to vent the funnel. Dichloromethane (including the emulsion) is then drained from the bottom into a 50mL Erlenmeyer flask. Same extraction process is repeated on the same filtrate and the dichloromethane is, once again, let out to the same 50mL Erlenmeyer flask as before. The combined dichloromethane solution and water (20mL) is poured into a rinsed separatory funnel. Mixture is gently swirled and drained out into an Erlenmeyer flask. Anhydrous magnesium sulfate is added to dehydrate the washed mixture. The solution is then filter into a weighed, dry, 100mL Erlenmeyer flask. Dichloromethane in the mixture is vaporized with a rotary evaporator. The Caffeine, white powder residue, (0.0486g) should be obtained. Results Caffeine: C8H10N4O2 Description: a white tasteless

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