Aspirin is a painkilling drug and is produced worldwide to reduce and stop pain. Aspirin is made up of ehtanoylation of 2-hydroxbenzenecarboxylic acid in a presence of phosphoric acid. AIM: The aim of the experiment is to prepare and produce aspirin as pure as possible. I will do this threw preparing the aspirin and purifying the product threw recrystallization. I will then obtain a melting point of my product to get an estimate of its purity. By the end of the experiment the target is to produce aspirin as pure as possible. Apparatus for synthesis of aspirin Materials for synthesis of aspirin.
Production of Aspirin Method 1) Weigh out around 2. 0g of hydrobenzenecarboxylic acid 2) Put 4cm3 of ethanoic anhydride into a pear shaped flask 3) Add the 2 –hydroxbenzenecarboxylic acid to the pear shaped flask a well and mix. 5) In a fume cupboard, add 5 drops of phosphoric acid to the reaction mixture in the pear shaped flask and swirl to mix 6) Set up a flask with a reflux condenser 7) Without cooling, add 2cm3 of water down the condenser. This will react with any excess ethanoic anhydride in a vigorous reaction. This will allow the product to become more pure.
8) When the reaction of the excess ethanoic anhydride with water has finished, pour the mixture into 40 cm3 of cold water in a 100 cm3 beaker and allow cooling to room temperature. 9) Complete crystallization by placing the beaker and its contents in an ice bath. If necessary scratch the sides of the beaker with a glass rode to induce crystallization. 10) Collect the product by suction filtration and wash with a little water. Suction and filtration involves filter paper and a funnel for the excess impurity’s to drain out.
Evaluation of production of aspirin The experiment went overall well, and the production of aspirin went to plan. We were able to use all the apparatus and measure out materials independently and accurately. The crystals where perfectly formed and we gained a large amount. The only problem was when filtering out the product we forgot to add filter paper . This may have reduced purity and left unwanted products , so next time we carry out the experiment we shall insure we use filter paper.
Also we will cool the aspirin more slowly to increase the crystals size. I would estimate that my product is 95 % pure because we measured and carried the experiment out correctly. Although not using the filter paper may have created a few unwanted products in are aspirin making it impure by 5%. Melting point 1) To check the purity of my aspirin I will check the melting point of my synthesized aspirin and compare with the commercial one by TLC.
To do this I will take a small amount of the purified compound and crush it down in a capillary tube and place it in the melting apparatus that has been preheated to 120 degrees then record to the temperature to which it melts ,from when the crystals begins to soften and the temperature at which the last solid disappears 12) Then to a clean test tube add about 10 mg of recrystallized aspirin from my own product, slowly melt and check melting points. And then compare the two and see the melting points. Melting points of aspirin (pure aspirin melts at 135 degrees) Aspirin Type| Melting point| Difference in the two melting points.
Pure or not| Pure aspirin| 135 degrees| pure| Tesco brand aspirin| 135 degrees| pure| Synthesised aspirin | 134 degrees| impure | Evaluation The experiment on the melting points went well although it took some time to collect the aspirin in the capillary tubes and we did not measure the aspirins out equally. This may have affected the melting points making the data unreliable; however the data shows similarity between the two products reassuring they are equally the same. Next time I carry out the experiment I will use bigger capillary tubes allowing me to collect the aspirin more efficiently.
We only melted the recrystallized aspirin and Tesco aspirin once, this is not an accurate set of results and next time should be melted 3 times using the same product and then check to see if the set of data is the same and reliable. Conclusion The data shows that the Tesco brand melts at 135 degrees and that relates to pure aspirin. Pure aspirin melts at 135 degrees and my recrystallized synthesised melted at 134 degrees, this shows me that that my aspirin is impure and contains a small amount of impurities. My aspirin melts at 1 degree less than pure aspirin.
This therefore shows there are different products in my aspirin that have a different melting point to pure aspirin. To work out a estimates of how pure my substance is I have come up with a percentage. 100/135 =0. 74 % x 134 = 99. 16 % pure aspirin and 0. 84 % impure substances Chromatography method On a watch glass place a small amount of my recrystallized aspirin and on another place the crushed Tesco pure aspirin. Label both of them and dissolve each one in small amount of DCM.
Using capillary tubes on the TLC sheet put four spots (drops) from the capillary tubes on the thin layered chromatography paper, 3 of which are my recrystallized aspirin and one Tesco brand. Then place the TLC in a chromatography tank which contains a solute which is ethanol dichloromethane. Then leave the solute to set in and then allow drying and recording and checking results. Labelling the TLC paper Line 1 cm from top where solute ends Line 1 cm from top where solute ends | Line 1cm from bottom of filter paper where the products are dropped on. Line 1cm from bottom of filter paper where the products are dropped on. | | Tesco brand aspirin Tesco brand aspirin.
Recrystallized aspirin Recrystallized aspirin The experiment for chromatography went overall well and the TLC was labelled accurately and the products were plotted correctly. Although we plotted one of the points 1 mm of the line so when doing the calculations we had to re arrange the sum. During the practical we realised that the TLC paper is very fragile and can be ripped or stained easily. My results showed that. From the line to distance solvent travelled Recrystallized Aspirin =11. 5 cm Recrystallized Aspirin =11. 5 cm Recrystallized Aspirin =11. 5cm Tesco pure aspirin=11. 6 cm The distance the solute travelled=12. 3 cm.
Distance solute travelled /distance solvent travelled =RF VALUE RF value Recrystallized Aspirin=11. 5/12. 3= 0. 93 Tesco pure aspirin=0. 94 The data shows that the pure aspirin and my recrystallized aspirin have no major difference and that my aspirin has a slight impurity. The impurity is not a large amount and the pure aspirin has a RF value of 94 and mine has a RF value of 0. 93 that’s only 0. 1 difference showing that my aspirin is near enough to pure. Overall my aspirin only has a few impurities and next time if I follow the mistakes and correct them e. g. the filter paper, I should be able to get pure aspirin and better results.