Analysis Of Aspirin

Synopsis

The general objective of this experiment was for the students to familiarise with the preparation of a simple organic compound and to purify the compound by recrystallization. This experiment allows the students to conduct synthesis of aspirin, reinforcing the skills of recrystallization and the technique of melting point determination.
Esterification was used to synthesize aspirin which was by reacting salicylic acid with acetic anhydride. To speed up the reaction, dehydrating agent and conc. sulphuric acid was present. The purity of a substance, which is the aspirin in this particular experiment, can be determined by the identification of its melting point.
Both experimental successes and errors were analysed. The mass of aspirin

The aspirin crystals were packed into 3 small capillary tubes to ensure that they are compressed so as to prevent any air gaps. Subsequently, the aspirin crystals that are in the 3 capillary tubes are placed into the melting apparatus and the temperature range was recorded. Since the range is quite far from the theoretical value of 140°C, aspirin's purity attained was low due to impurities present. One potential reason is because of the swift cooling. When the aspirin is left to cool, the crystal lattices will form too rapidly which will surround other molecules thus making the aspirin impure. Another reason could be because the recrystallized aspirin has not dry completely and there might me left over solvent that will affect the temperature range of the aspirin.
From the both derived calculations, the aspirin obtained is relatively pure. This result could be due to possible experimental errors or inaccurate techniques performed which led to a percent yield that is not up to expectation. Furthermore, the reaction might not have been completely reacted or the salicylic acid in the solution of acetic anhydride and concentrated sulphuric acid did not dissolve completely when it was being heated. These factors might affect the overall results of the aspirin yield