Aspirin has many pharmaceutical uses; the most important is the cure for any kind of pain. It can also treat arthritis because it has an anti-inflammatory effect and also reduce fever. One of the majors side effects gastritis this gives stomach aches.
Melting Point apparatus
Observations
- At the start of the practical we had to add 3 grams of salicylic acid to a weighing boat and then weight it. The salicylic acid is like a white powder.
- Once I measured the salicylic acid and the weighing boat after this I had to add it to 6ml of acetic anhydride once I add this no reaction took place but there was a colour change which changed from see through.
- Before the acetic anhydride was added and now it has turned cloudy once the acetic anhydride was added. The only observation I can pick out from acetic anhydride was the smell, it smelt like vinegar it might mean that this could be used in the process of alcohol.
- After the two has turned cloudy you will place them in a hot water bath then once in the hot water it will become see through and also the vinegar smell gets stronger.
- I started to add drops of water into the beaker nothing happened but when I added 20ml of cold water it had a quick reaction when I added it had a white emulsion for couple of seconds and then went away.
- Once I place the beaker in the cold water after about 10min it started to crystallize. Once crystallized I had to put it in this machine where it sucked out the excess water.
- When I left it over night it turned into crystals, to see if this was pure we had to do the Iron III chloride test. When I added 2-3 drops of this to my aspirin it turned purple this showed us that phenol derivative is present.
Aspirin Percentage Yield Calculation Sheet:
1) Write a balanced chemical equation for the synthesis of aspirin:
C7H6O3+C4H6O3 --> C9H8O4+C2H4O2
2) Calculate the molar mass (Mr) of 2-hydroxybenzoic acid (C7H6O3)
Carbon + Hydrogen + Oxygen = 138g/mol
(12.01 x 7) (1.0079 x 6) (16 x 3)
84.7 6.047 48
3) Using the mass of 2-hydroxybenzoic acid you used in your experiment, calculate the number of moles of 2-hydroxybenzoic acid used in your experiment.
Moles of 2-hydroxybenzoic 3 = 0.0217mol
138
4) Assuming that all of the 2-hydroxybenzoic acid is converted into aspirin, deduce the number of moles of aspirin produced in theory (Theoretical yield)
Salicylic acid (138 g/mol): limiting reactant: Acetic Anhydride
0.003kg = 3g
3g / (138 g/mol) = 0.0217 moles molar mass of aspirin x acetic anhydride moles =
Theoretical yield
180.157 x 0.0247 = 4.45g
Acetic Anhydride (102 g/mol):
6ml= 2.52g
2.52g / (102 g/mol) = 0.0247 moles
5) Calculate the molar mass (Mr) of aspirin (C9H8O4)
Carbon + Hydrogen + Oxygen = 180g/mol
(12.01 x 9) (1.0079 x 8) (16 x 4)
108 8.06 64
6) Using this and the mass of aspirin obtained in your experiment, calculate the number of moles of aspirin produced (Actual Yield).
Moles of aspirin = 1.07 = 0.00594mol
180
7) Calculate the percentage yield of your preparation.
1.07 x 100 = 24%
4.45