EXTRACTION OF CAFFEINE
Caffeine (C8H10N4O2) is the common name for
1,3,7-trimethylxanthine or 3,7-dihydro-1,3,7-trimethyl-1Hpurine-2,6-dione. Caffeine is naturally produced by several
plants, including coffee beans, guarana, yerba maté, cacao beans,
and tea. For the plants caffeine acts as a natural pesticide. It
paralyzes and kills insects that attempt to feed on the plants. The
molecule was first isolated by the German chemist Friedrich
Ferdinand Runge in 1819.
When purified, caffeine is an intensely bitter white powder. It is
added to colas and other soft drinks to impart a pleasing bitter note. However, caffeine is also
an addictive stimulant for central nervous system, heart rate, respiration...
A normal dose of caffeine is generally considered to be 100 mg, which is roughly the amount
found in a cup of coffee. However, more than half of all American adults consume more than
300 mg of caffeine every day, which makes it America's most popular drug.
Extraction:
Tea leaves consist mostly of cellulose (a water-insoluble polymer of glucose), caffeine and a
small amount of chlorophyll.
The solubility of caffeine:
In water is ( Density = 1 g/mL ):
 22 mg/ml at 25·C
 180 mg/ml at 80·C
 670 mg/ml at 100·C.
In dichloromethane :140 mg/ml at 25·C. ( Density = 1.3 g/mL )
Place 30 g of the tea leaves in 250 mL of distilled water and 5 g of sodium carbonate in a
beaker and boil for 10 minutes. Filter the cooled solution then transfer the filtrate into a
separating funnel and extract using dichloromethane. After extraction, remove the lower
organic layer and add in it anhydrous sodium sulphate. The sodium sulfate will remove any
water and water soluble salts that are retained in the dichloromethane. Filter to remove the
solid sodium sulphate and evaporate the solution by boiling it on a water bath. The residue
will be crude caffeine.
Vocabulary:
Bitter: amer
to impart: pour donner, obtenir
mood altering: changement d'humeur
crude : pure
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