Extraction of Caffeine

Topics: Solubility, Solvent, Water Pages: 2 (789 words) Published: May 7, 2012
In this experiment, Caffeine was extracted from a commercial tea bag through solid-liquid extraction, and then further purified through sublimation. To begin the extraction, the commercial tea bag containing ~55mg of caffeine was placed in a mixture containing 2.2g of anhydrous sodium carbonate along with 20 ml of D.I. water. The sodium carbonate was placed into the solution to keep the caffeine from becoming slightly acidic(protonated), which would prevent the caffeine from being able to be separated once the organic solvent (dichloromethane) was added to the solution, as a charged species dissolves in the aqueous layer while a neutral species goes to the organic layer. The caffeine also dissolves in the organic layer due to similar intermolecular forces with dichloromethane. Once the organic solvent was added, the solution was centrifuged to get rid of the emulsions and the bottom organic layer containing the caffeine was extracted. The reason the organic layer was at the bottom is because dichloromethane is denser than water, causing the aqueous layer to float towards the top. This extraction method was done a total of four times to ensure that most of the caffeine was able to be extracted from the aqueous layer. To make sure that no water was present in the extracted solution, the solution was ran through a glass funnel that contained 2.5g of the drying agent anhydrous sodium sulfate. The sodium sulfate crystals bind to any water molecules present in the solution and form crystalline hydrates in the funnel while the dry caffeine is extracted into a flask. The dry caffeine was then evaporated on a hot plate and the crude product was recovered with a percent recovery of 193% (106mg). As the results show, the crude caffeine product was much higher than the amount of caffeine that was contained in the commercial tea bag (55mg). This means that the product that was recovered still contained impurities and needed to be further purified. This...
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