The Synthing Point Of Aspirin

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The objectives of this experiment are to carry out the process of synthesising aspirin and reinforce both the skills of recrystallisation and melting point determination. In this experiment, we are supposed to measure the amount of aspirin collected to calculate the percentage yield of aspirin. Apart from that, we are also required to find the melting point of aspirin.


1.1: aspirin

Aspirin, also known as acetylsalicylic acid, is an aromatic compound containing both a carboxylic acid functional group and an ester functional group. Aspirin, being a monoprotic weak acid, is only slightly soluble in water and it can be prepared by reacting salicylic acid and acetic anhydride in the presence of an acid catalyst.

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Next, 30ml of hot distilled water was added once the solid is dissolved. If a solid is formed at this point, 1ml of ethanol was added again and warm until it dissolves completely. The solution was left to cool to room temperature before putting it in an ice bath. A clean, dry watch glass together with 2 pieces of filter paper was weighed and its weight was recorded. Suction filtration was carried out using the weighed filter paper to obtain the recrystallised product. The crystals and filter paper was then transferred onto the weighed watch glass and dried in the oven for 15 to 20 minutes, followed by placing it into the desiccator for 5 to 10 minutes. The dried crystals together with the filter paper and watch glass were weighed and the weight was recorded. After which, the weight of dried, recrystallised aspirin was calculated. Lastly, the percentage yield of dried, recrystallised aspirin was …show more content…
The literature percentage yield of aspirin in this experiment is >50% and the experimental percentage yield that was obtained is 46.0%. This 46.0% obtained is relatively low and this can be caused by some sources of error. During the procedure, while making sure that the solids have completely dissolved, we realised that we have small black solids in the solution. Initially thinking that it might be the undissolved solids, we added slightly more ethanol and warm it longer however, the black solids did not disappear. This could be due to impurities on the glass rod used to stir the mixture or the unclean conical flask from the previous class therefore causing the low percentage yield. It could also be due to the remaining crystals that are left on the side wall of the conical flask that are not being washed down thus causing the low percentage

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