In this experiment, aspirin is to be prepared via an esterification reaction and purified through recrystallization. The purity of the synthesised aspirin is determined through melting point determination.
One of the most widely used medicine is aspirin. It is best known for its pain relief for mild headaches, toothaches and muscle aches. It also acts as a nonsteroidal anti-inflammatory drug by providing relief to the swelling.
Salicin, an active ingredient in salicylic acid, was found to have medical benefits in the 1973. However, the phenolic and carboxylic acid functional groups in salicin caused irritation in the mouth and stomach lining. In 1937, a German chemist of a Bayer pharmaceutical company developed a more…show more content… Figure 1 shows the reaction between salicylic acid and acetic anhydride to produce aspirin and acetic acid.
Esterification is a chemical process to produce compounds with the functional group –COO- known as esters by reacting carboxylic acid with alcohol with the removal of a water molecule. The reaction occurs only if the mixture is heated with a few drops of strong acid catalyst. The reaction is slow and reversible.
A solvent pair (ethanol and water) is used in this recrystallization experiment. If a single solvent cannot be used for recrystallization, a solvent pair is used to solve the problem. Ethanol helps dissolve aspirin however it dissolves impurities at the same time. The water helps in recrystallizing aspirin only, thus leaving behind impurities.
Recrystallization is used to purify impure compounds in a solvent. The process is based on the principal that solubility of solids increases with increasing temperature. The main processes of recrystallization includes dissolving the solute in the solvent and filtering out the excess solute. The filtrate is heated until saturated and left to cool in the open air then in an ice…show more content… In this experiment, the technique is used to collect insoluble aspirin crystals in a recrystallization process. The filtrate is poured into a Buchner funnel with filter paper placed in it connected to an aspirator. The solvent is forced through the filter paper by the suction of the vacuum, leaving behind the insoluble crystals. The collected crystals are placed in an oven followed by a desiccator. Figure 2 shows the set-up of vacuum filtration. This procedure is more effective than gravity filtration which involves using a glass funnel with filter paper lined in it as vacuum filtration takes a much faster time to complete the process.
Percentage yield is the amount of product obtained in the experiment. Percentage purity is calculated using the formula, mass of pure product / mass of impure product x 100%. Therefore, if the percentage yield is high, the percentage purity would increase. The percentage yield of aspirin in this experiment is 49.7 %. According to the results, the percentage yield is rather low and the aspirin obtained may contain impurities.
The percent error can be calculated using the formula, (experimental mass - theoretical mass) / theoretical value x 100%. The percent error of this experiment is -50.4%. Since the percent error is a negative error, this indicates that the percentage yield is