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Isolation of Caffeine from Coffee

Date of laboratory work:

10/9/2012

5:00-7:45

Date of report written:

10/15/2012

Introduction:

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 …show more content…

* The coffee became lighter brown and cloudy after CaCO3 was added.

| Color of organic (bottom) layer | Color of aqueous (upper) layer | CH2Cl2 added | Yellowish with bubbles | Dark brown | MgSO4 added | Light yellow with clumps | | After vacuum filtration | Bright yellow | | After rotary evaporation | Became dry, yellowish on flask wall | |

* The final caffeine amount we collected was 0.31g in a white powdered form. * The melting point temperature was 217-222 °C.

Calculation of weight percentage:

Using equation 1: weight percentage of caffeine=(0.31g20.08g)*100= 1.5%

Discussion:

1. Why was the sodium carbonate added in Experiment 11b?
Sodium carbonate was added to the solution because, when tennis are extracted into water, some of the compounds are partially hydrolyze to form acid. Therefore, the addition of sodium carbonate helps the acid to convert to their sodium salts, which are highly soluble in water

2. What are some possible explanations for why the melting point of your isolated caffeine may be lower than the literature value (236)

This may because of the isolated caffeine produced by the experiment was containingother elements which cause the caffeine not 100% pure. Thus, lower the melting point of the caffeine.

Your caffeine was not pure and probably