Chem 243a - Isolation of Caffeine from Tea or Coffee

Chem 243a - Isolation of Caffeine from Tea or Coffee - 5A...

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5A: Isolation of Caffeine from Tea of Coffee Antonio Alarcon Chem 243a 9/28/07 I. Abstract In this lab, caffeine was extracted from the structural components of tea leaves and purified by the process of sublimation. The lab concluded the following: 10% of pure caffeine was recovered from the tea, while 40% of pure caffeine was recovered from the extracted crude caffeine.
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II. Introduction In this lab, we were to isolate caffeine from tea leaves (or coffee) through a sequence of extractions and purify it by the means of sublimation (a process by which a solid is evaporated into a gas). This experiment demonstrated several techniques: separation, extraction, anhydrous drying, evaporation, and sublimation (Padias, 40, 41). Of the techniques presented in this lab, extraction and sublimation were of utmost importance. Although these two processes seemed fairly straight forward, the components of tea leaves complicated this process (to some extent). As described in the lab manual, tea leaves consist of the following: cellulose, tannins, pigments/chlorophylls , and caffeine . Yet, as we now know from previous labs, one can easily separate samples by the means of solubility. Due to the fact that we are isolating caffeine with dichloromethane (a moderately polar solvent), it can be assumed that tannins have the highest polarity followed by pigments/chlorophylls, caffeine, then cellulose (these polarities were designated by the number of present carbonyl groups and overall dipole-dipole interaction).
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