Isolation of Caffeine from Coffee
Date of laboratory work:
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The purpose is to isolate caffeine from coffee by using the organic solvent dichloromethane (CH2Cl2) that is also referred to as direct contact. Calcium carbonate (CaCO3) is used to remove the tannins from the coffee. Afterwards an extraction is used to separate the organic layer (bottom) from the aqueous layer (upper). By using a rotary evaporator, it evaporates the organic solvent and forms the crude caffeine. Afterwards we used acetone-petroleum ether for recrystallization and the vacuum apparatus for filtration to obtain pure caffeine. At the end the melting point of the pure caffeine was obtained.
(Reference: Organic Chemistry Laboratory Manual)
We used 250 mL of water and 20.08 g of pre-ground coffee in the espresso maker to make the coffee. After we collected the coffee into a beaker that had a 6.0 g of CaCO3 in it. We heated the mixture to about 70 °C for about 10 minutes on a hot plate and the let it to cool down to room temperature. Then we used the fritted funnel with Celite, which is a filter aid inside the filter for filtration. If foaming occurred, vacuum had to be removed right away until foaming disappeared.
Afterwards, the filtrate was transferred evenly into 2 separatory funnels, and extracted with 4*20 mL of dichloromethane (CH2Cl2). The separatory funnels were rolled carefully and not shaken. After the extractions, the organic (bottom) layer was collected. The combined organic layer then was dried with anhydrous magnesium sulfate (MgSO4). The insoluble solids were filtered and removed. The filtrate then was transferred into a 250 mL round-bottom flask. Then a rotary evaporator was used to evaporate the solution. This then formed the crude caffeine.
The crude product was recrystallized with...