Extraction of caffeine from tea bags
Procedure:
Solvent extraction is used to isolate and purify caffeine from tea bags.
In order to determine the amount of caffeine in tea, a series of techniques are performed.
Sodium carbonate, CH2Cl2, a drying agent in the form of calcium chloride is used in various steps for extracting caffeine from tea bags.
Purity of caffeine can be increased by sublimation because it goes straight from the solid to vapor form, and then recrystallizes again after bypassing the liquid form once more.
Result:
Following result we will get in extraction of caffeine from tea bags.
Weight of the flask - 29.578 g
Weight of dichloromethyl/caffeine solution - 4.960 g
Weight of flask and caffeine product - 29.643 g
Weight of caffeine product - .065 g
Theoretical mass of Caffeine (1 bag) - 055 g (2 bags used)
% error = expected - actual x 100
expected
= 0.12 -0.063 x 100
0.12
= 47.5%
% Recovery = actual x 100%
Expected
= 0.063 x 100%
0.12
= 52.5%
Extraction of paracetamol
Paracetamol can be taken in a number of ways and can be bought in many different formulations. Common ones are tablets (500 mg), fizzy dispersible tablets (500 mg), paediatric oral solutions (1 20 mg/5 cm3), oral suspensions (250 mg/cm3), and suppositories (1 25 mg). It is also sold in capsules as a mixture with other active ingredients such as codeine and caffeine. Work in small groups and discuss why there might be advantages in having a number of formulations. Comment on the doses available and suggest a target group for each one. Present your findings to the group, perhaps as a poster or as an audio-visual presentation e.g. Powerpoint presentation.
This process relies on the fact that paracetamol is not very soluble in cold water (1.4 g/lOO cm3) but very soluble in hot water (5 g/100 cm3). When the crude solid is heated in water it will dissolve and any insoluble impurities can be filtered off. The soluble impurities will also of course dissolve. When the hot solution is cooled down, it reaches the temperature at which paracetamol reaches its limit of solubility and therefore starts to crystallize out. However, the soluble impurities are only present to the level of a few percent and so never reach their limit of solubility and thus stay in solution.
When 4-aminophenol is treated with acetic anhydrate it produces paracetamol.
Following balanced equation of the reaction taken place.
C6H7NO + C4H6O3 --> C8H9NO2 + C2H4O2 (acetic acid)
4-aminophenol + acetic anhydrate → paracetamol + acetic acid.
We will perform the extraction of paracetamol from the unknown product accordingly and by the mass of product obtained we will calculate the purity of paracetamol.
Let us suppose we get the following result.
Approximately 1.09 grams of 4-aminophenol was measured out to use in the experiment. This is (1.09/109.13) = 9.99 x 10-3 moles of acetic anhydrate which should result in the same amount of moles of paracetamol, as these are created in a 1:1 ratio.
The theoretical yield is (9.99 x 10-3 x 151.17) about 1.51g of paracetamol which is the amount that should be received.
The actual yield at the end was 1.05g which is ≈ 70 % (69.54 %) (1.05/1.51 x 100) of the theoretical amount.
In practice it is impossible to receive the total theoretical yield (100%) as some molecules or atoms will be lost in the process.
For synthesis of aspirin from salicylic acid we need to consider balanced reaction and known mass of reactants and product.
Salicylic acid + acetic anhydride → aspirin + acetic acid
138 g/mol 102g/mol 180 g/mol 60 g/mol
Mass of desired product = C9H8 = 180 g/mol
Atom economy = Mass of desired product ×100
Total mass of reactants
= 138 ×100
240
= 57.5%
