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Synthesis of Aspirin

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The aim of this practical is to carry out a chemical reaction between salicylic acid with anhydride. This will allow us to calculate the percentage yield. The chemical company for which you work has developed a new laboratory method for synthesising aspirin which produces a high yield of pure product. Before investing the large amount of money it would take to scale up the process for mass production of aspirin, the directors want to know if this new method is significantly better than existing methods, in terms of the percentage yield and purity of aspirin produced. Theory Aspirin, which is sometimes called acetylsalicylic acid, was first made in 1893 by a German chemist Felix Hofmann. Aspirin is classified as organic ester and organic acid. It is mostly used in medicine like pain killers and also they are used for reducing fever. ...read more.


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. ...read more.


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 ?? ?? ?? ?? Nahom Efrem 16/06/2009 Synthesis of Aspirin ...read more.

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