chem lab 4 - Hoang 1 Phuong Hoang Chem 3105 541 10/01/08...

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Hoang 1 Phuong Hoang Chem 3105 – 541 10/01/08 Experiment 4: Isolation of a Natural Product: Extraction of Caffeine from Tea I. Purpose: The purpose of this experiment is to isolate caffeine from tea leaves and then to purify it. II. Background: Caffeine, or 1,3,7-trimethylxanthine and its close relative theobromine both possess the oxidized purine skeleton. These compounds are classified as pseudoalkaloids, since the only nitrogen atom at the 7 position can be traced to an amino group originally derived from an amino acid. We will simple treat caffeine as an alkaloid. Caffeine is readily soluble in hot water, so it is easy to separate caffeine from black tea leaves by aqueous extraction. Other substances are also present in the tea leaves and are also water soluble. The addition of Na 2 CO 3 , a base, during the aqueous extraction helps to increase the water solubility of the acidic substances by forming ionic sodium salts and liberating the free base. When adding methylene chloride, in which caffeine has a moderate solubility, the
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chem lab 4 - Hoang 1 Phuong Hoang Chem 3105 541 10/01/08...

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