Extraction of Caffeine from Tea Leaves
Caffeine is soluble in boiling water and as a result it is easily extracted from tea bags by steeping in hot water. This process leaves behind the water insoluble portions of the tea bag. However, water extracts more than just caffeine, so a final separation is done with an organic solvent that will dissolve primarily caffeine. The organic solvent used in this experiment is Dichloromethane (CH₂Cl₂). Dichloromethane is less polar than water and this difference in polarity allows the separation. Extraction of the tea with the Dichloromethane, followed by evaporation of the organic solvent leaves crude caffeine, which on sublimation yields a relatively pure product. Sublimation is the transition of a substance from the solid phase directly to the gas phase without undergoing intermediate liquifications. This process is preferred over recrystallization because it is better at removing impurities. Experimental
For this extraction experiment two bags of tea were used, which is approximately 4 grams of tea. Water was heated in a small beaker until it began to boil. It was then removed from heat and 2 grams of Na2CO3 was added and dissolved. Finally the loose tea was added to the water and allowed to steep for 5 minutes. After 5 minutes the mixture was put through a suction filtration. A suction funnel was secured on top of the suction flask with the vacuum tubing. No filter paper was used because the tealeaves were very course. Then 400mg of NaCl was added and dissolved. The solution was then cooled in an ice bath. The solution was then transferred into a separatory funnel and was washed 3 times using 5 ml portion of CH2Cl2. CH2Cl2 formed a separate layer on the bottom of the flask and was drained into a 25 ml flask after each wash. Each wash was gently swirled to prevent emulsion. The combined washes were then dried using small portions of Na2SO4 two times to remove any water. A suction...
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