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Aim To produce synthetic aspirin. To calculate the percentage yield of the aspirin produced. To compare the aspirin produced in the lab with tablet aspirin and aspirin from the lab by there melting points

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Introduction

Preparation of aspirin Introduction Aspirin is a human-made, synthetic version of salicylic acid, used to reduce fever and inflammation and relieve pain. Originally sold as a powder, and now in tablets, aspirin was a trademarked name until 1921. Researchers keep finding new ways that aspirin promotes and protects human health It is an ester and can be prepared by the condensation reaction between 2-hydroxybenzoic acid (or salicylic acid) and Ethanoic anhydride. Purity of aspirin can be checked by determining its melting point. Aim * To produce synthetic aspirin. * To calculate the percentage yield of the aspirin produced. * To compare the aspirin produced in the lab with tablet aspirin and aspirin from the lab by there melting points Method Glassware Chemicals Conical flasks Measuring cylinders 2- hydroxybenzoic acid Beakers Thermometers Ethanoic anhydride Dropper Hot plate Conc. Sulphuric acid Balance Buchner funnel and flask Ethanol Vacuum pump Clock glass Anti-bumping granules Oven Melting point apparatus Deionised water Capillary tubes Stirring rod Ice > A 50 cm3 conical flask was weighed and ~10g of 2- hydroxybenzoic acid was added. ...read more.

Middle

> The crude product was transferred to a 100 cm3 conical flask containing ~20 cm3 of ethanol. A couple anti-bumping granules were added and the mixture was gently heated on a hot plate until the solid dissolved. > The solution was poured into a 100 cm3 conical flask containing ~ 50cm3 of deionised water. Oil formed, so the mixture was reheated on a hot plate to dissolve it. It persisted so a few drops of ethanol were added and the mixture was reheated. > The mixture was set aside and allowed to cool to room temperature. > The crystals of aspirin were filtered of using a vacuum pump and washed of with a small volume of cold water. Air was drawn through the crystals for a few minutes to allow them to partially dry. > A clock glass was weighed and the crystals were transferred on to it. The crystals were dried in an oven at about 100 oC and then the clock glass and crystals reweighed. ...read more.

Conclusion

This process can be helped by leaving the crystallising mixture in the dark, undisturbed. The melting point of pure aspirin is 138 - 140� C. The tablet aspirin which is sold in shops as medicine has a melting point of 151� C which is above pure aspirin, but this is because there are other compounds within the tablets. As for the high purity aspirin stored in the lab it has a melting point of 148� C which shows there are impurities in the compound. The synthetic aspirin produced in the lab is not pure aspirin as it melted at 147� C which is above the melting point for pure aspirin. The aspirin produced has got some impurities in it. Conclusion The aspirin produced in the lab is not pure aspirin as impurities are present as detected by the melting point. Due to human error and some of the desired compound was lost and along with the impurities in crystallisation. This made the percentage yield relatively low at only 33%. ?? ?? ?? ?? Jennifer Chr�tien page1 of 3 The preparation of aspirin Jennifer Chr�tien page1of3 ...read more.

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