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Date Submitted: 10/07/2014 03:57 AM
COURSE NAME : ORGANIC CHEMISTRY 2
COURSE CODE : CHM 556
NUMBER AND TITLE EXPERIMENT : 1. ISOLATION OF CAFFEINE FROM TEA BAG
OBJECTIVE :
To determine the yield, percent recovery and melting point of caffeine isolated from
tea bag.
INTRODUCTION :
Extraction process selectively dissolves one or more of the mixture compounds into a suitable
solvent. The solution of these dissolved compounds is referred to as the extract. In this
experiment, caffeine is isolated from tea bag. Here the organic solvent methylene chloride is
used to extract caffeine from the tea bag because caffeine is more soluble in methylene
chloride than it is in water. Caffeine is an analgesic drug that increases the heart rate. It exists
naturally inespecially tea and coffee. Caffeine constitutes as much as 5% by weight of the
leaf material in tea bags. Although chlorophylls are soluble in methylene chloride, most
other substances in tea are not. Thus, the methylene chloride extraction of the basic tea
solution removes nearly pure caffeine. The methylene chloride is easily removed by
evaporation in which the boiling point of methylene chloride is 40°C to leave the crude
caffeine. Sodium carbonate was also added to the mixture. This was done to form a sodium
salt derivative of tannin compounds contained in tea. Tannins also dissolve in hot water used
to extract caffeine. Tannins are a class of compounds that have certain properties in common.
Tannins have a phenolic group and also hydrolyzes to form an acid. Because of their phenolic
groups and acid formation after hydrolysis, they can react with sodium carbonate to form a
salt. The salt is soluble in aqueous solution ,therefore, it does not separate into the organic
layer. The organic layer separates to the bottom because methylene chloride is denser than
water. Tannins are usually divided into two classes which is those that can be hydrolyzed
(react with water) and those that cannot be hydrolyzed....