Experiment 4 – Chem 276 – Fall Semester 2010 Page 1 of 3
Caffeine extraction from Coffee
Introduction
First isolated from coffee in 1820, caffeine has become the most widely used legal drug
in the world. It is estimated that ninety percent of those living in the United States use
the drug through the consumption of coffee, tea, soda or over the counter drugs like
Vivarin. Caffeine is found occurring naturally in tea leaves, coffee beans, cola nuts, maté
leaves and the guarana plant. A white crystalline powder with a melting point of range of
234 to 236.5 C, caffeine has the chemical name of 1,3,7-trimethylxanthine. Caffeine is
an alkaloid, meaning that it is an organic molecule containing nitrogen which has
pharmacological effects on humans and animals. The chemical structure is shown below.
N
N
CH3
CH3
O
O
N
N
CH3
H
Commercially, caffeine is obtained as a by-product from the decaffeinating process of
coffee. Caffeine is known to have a bitter taste and is used by Barq’s as a flavoring to
add a sharp bitter taste to their root beer. The list below shows the amount of caffeine in
a 7 oz. cup.
Brewed coffee 80-135 mg
Brewed tea 40-60 mg
Espresso 350-460 mg
Caffeine is a stimulant of the central nervous system, cardiac muscle and respiratory
system. It also acts as a diuretic. An overdose of caffeine can cause headaches, muscle
tremors and insomnia. Ten grams is considered to be a lethal dose.
When coffee is brewed, caffeine is dissolved into the water along with tannins. These
tannins are what give the coffee its dark color. Since we are focused on isolating only
caffeine, the tannins need to be removed. The addition of Na2CO3 reacts with the tannins
to form a salt. These salts are soluble in water but are insoluble in an organic solvent
such as chloroform. Even though caffeine is soluble in water to the extent of 1 g per 46
mL, caffeine is more soluble in chloroform to the extent of 1 g per 10 mL. Therefore,
caffeine can be extracted by chloroform from the aqueous mixture leaving behind the
tannin salts. Evaporation of the chloroform leaves behind the crude caffeine solid.
