Isolation of Coffee from Tea

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....