Organic Chemistry Caffeine Extraction Lab ( Tea Bags )
To demonstrate the isolation of a natural product from a biological source (tea bags) using extraction techniques, and to demonstrate purification by sublimation. In a 400ml beaker, 15 tea bags were submerged in approximately 125ml of water. This was brought to a boil over a bunsen burner and allowed to boil for about 15 minutes.The tea bags were removed from the tea infused water and discarded. 15 grams of Na2CO3 was dissolved in the tea water by stirring, and allowed to cool. It was then transferred into a reparatory funnel. 20ml of Methylene chloride was added and this mixture was shaken gently. The two distinct layers were separated using the "water drop" technique and the aqueous layer was mixed and extracted with another 20ml of Methylene chloride. The organic extracts were combined in a conical flask and dried with about 1gram of anhydrous MgSO4. The solution was allowed to stand for about 10 minutes, and swirled occasionally to complete the drying. The Methylene chloride solution was gravity filtered into a small, pre-weighed beaker. The solvent was carefully evaporated to dryness and the beaker containing the crude caffeine was re-weighed to calculate the yield.
Caffeine is soluble in water because it has several polar and basic functional groups. It states that alkaloids are basic nitrogen-containing compounds of plant origin, many of which are physiologically active when administered to humans. Caffeine has lower vapor pressure and therefore will sublime only at reduced pressure, and around 180 degrees Celsius. What might have happened to your caffeine if you had tried to sublime it at atmospheric pressure? -If you increase the pressure, the caffeine wouldn't go into the vapor phase; to get the caffeine to sublime, the pressure needs to be lowered. These human errors caused the results to be inaccurate, and the percent recovery was negatively affected. Tea contains approximately 2% caffeine by weight. An alkaloid is defined as a basic nitrogen containing organic compound. For example, curarine, found in the deadly extract curare, is a powerful muscle relaxant; atropine is used to dilate the pupils of the eye; and physostigmine is a specific for certain muscular diseases. Assuming that you started with 25 g of tea leaves, calculate your percent recovery. During this lab, we used special equipment to lower the vapor pressure, in order for the caffeine to sublime. A few milliliters of the tea solution was accidentally spilled, and although the tea bags were boiled in water for 15 minutes, all of the caffeine surely didn't infuse the water, since they weren't completely dry before throwing them away. For substances with lower vapor pressure vacuum sublimation is used.
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