Using Recrystallisation Improve The Purity Of Aspirin Biology Essay

Using Recrystallisation Improve The Purity Of acetylsalicylic acid Biology EssayIn this experiment I have investigated the seek question How does the carry through of recrystallisation improve the naturalness of acetylsalicylic acid.I employ a well documented method of preparing aspirin. Having obtained the aspirin I per realiseed several recrystallisation litigatees on it. I then determined accurately the bar of aspirin in each of my strain by volumetric analysis. I was then able to determine worth and percentage yield by comparing it to an original digs Aspirin in the market. I also employ warming consign to assess ingenuousness.I learnt virtually Aspirin when we did the chapter medicine and drugs in our class. Aspirin is a very common drug delectation in our daily lives. The common chemical suck up wind isacetylsalicylic acidic. Salicylic acid was identified and isolated from the bark of a pass onow tree but it could non be synthesised in laboratory. In 1893 , Felix Hoffman Jr., a chemist ap spot out a practical way for synthesizing an ester derivative of salicylic acid, acetylsalicylic acid. Acetylsalicylic acid, a weaker acid than salicylic acid, was found to have the medicinal properties of salicylic acid without having the objectionable taste or producing the prevail problems as a side effect. The acetyl group effectively masks the acidity of the drug during its ingestion and after it passes into the small intestine, it is converted back to salicylic acid where it domiciliate enter the bloodstream and do its pain relieving action1. Acetylsalicylic acid is powerful as a pain reliever, fever reducer, and swelling-reducing drug but it also has faults, it causes potbelly irritation to nigh individuals and also may lead to Reye syndrome in young children. I was excited to see if this drug we use has the same purity when disposed(p) in lab and when bought from outside. Aspirin is an important analgesic therefore methods of improving purity are essential. The preparation of Aspirin involves organic synthesis and I learnt about this process when I studied organic chemistry and it an interesting topic to research about. The preparation of drugs that I use in my daily lives excited me peculiarly as I want to do biochemistry in university and also work in a pharmaceutical company for drug designing. Hence, I decided upon fashioning aspirin in the lab and researching about it.BACKGROUNG INFORMATION2.1 Synthesis of AspirinThe above is the answer for the formation of Aspirin. This organic synthesis is an esterification response between a compound containing a OH group (ester) and an acid. Esters are a type of organic acid in which the hydrated oxide groups are replaced. The H from the OH group is replaced by a carboxyl carbon C=O group.Esterification is theacid catalyzed reception of a carboxyl (-COOH) group and an -OH group of an alcohol or phenolto form a carboxylate ester. A catalyst is required for the react ion for example toilsome H2SO4.In the synthesis of Aspirin the -OH group is the phenolic -OHgroup attached to ring of the salicylic acid2.2.2 Purification of Aspirin using the process of recrystallisationI apply the process of recrystallisation to investigate how effective this process is in making Aspirin pure. The process of recrystallisation takes returns of the relative solubilities of contaminants compared to that of Aspirin3. The technique is to use a solvent in which the solid is sparingly soluble at low temperature and quite soluble at higher temperature (at the boiling point of the solvent). In my research Aspirin is insoluble in cold water and hence in the process of recrystallisation I branch dissolved Aspirin crystals into hot water and then let it cool down so that it would crystallize out. The solid is dissolved in the minimum quantity of solvent required to produce a re outcome at the boiling point of the solvent. Upon cooling the solution to room temperature or below, the solid crystallizes out of solution due to its lower solubility at the lower temperature4.Impurities (i.e., any foreign substance) in a solid are classified as soluble or insoluble. The removal of insoluble impurities is accomplished by filtering the hot solution. The insoluble impurities remain on the filter paper. Ideally, soluble impurities remain in solution when the solid world purified crystallizes. (Depending upon concentration and solubility of the impurity in the selected solvent it may sometimes be necessary to recrystallise more than one time. That is some of the soluble impurity cogency also crystallize. If any soluble impurity crystallizes, the resolve point of your product ordain be depressed). When recrystallisation is complete the purified solid is isolated by filtration and the crystals are rinse with a small quantity of cold solvent (to rinse off the solution of soluble impurities coating the freshly filtered solid)5.2.3 Determination of purity using run point apparatusI also utilize thaw point determination to give further evidence towards the purity of aspirin. Melting point is a useful measure for the purity of a solid. Melting point apparatus is commonly used for this purpose. It consists of a heated metal block with holes for a thermometer and melting point tubes. The hairlike tubes are provided open-ended and the perspicuous solid atomic number 50 be transferred into the tube and forced to the bottom with gentle tapping. The compound is heated belatedly especially around its melting point for accuracy.There are pleasing forces (intermolecular interactions) between the molecules in a solid that keep them together in an consistent crystalline structure. If enough heat energy is added to the solid the internal kinetic energy of the molecules causes them to move in the solid. At the temperature where the energy of molecular motion everyplacecomes the attractive forces between molecules the compound begins to melt. W hen a solid is pure the molecules are all identical and thus the interactions between molecules are similar and thus the sample leave alone melt at a distinct temperature. Impure compounds, on the other hand, have a range of intermolecular interactions between molecules and will melt over a range of temperatures.63. APPARATUS7-3.1 EquipmentsThe apparatus listed below does not list quantities for repeat developments.Conical flaskful (100 cm3) (-1)Measuring cylinders (10 cm3) (0.5cm3) (-2)Beaker (100 cm3) (-2)Glass rod (-1)Vacuum filtration flask (-1)Rubber tubing for vacuum flask (-1)Hirsch displace (-1)Water bath containing crushed ice (-1)Source of hot water (-1)Test-tubes (-4)Meltemp apparatus for finding the melting point of AspirinBurette (50cm3) (-1)Clamp stand (-1)Spatula (-2)Watch glass (-1)Melting point capillary tube (-1) perk paper to fit Hirsch funnel (-1)3.2 Chemicals2-hydroxybenzoic acid (salicylic acid) (2g)Ethanoic anhydride (4cm3)Concentrated sulfuric acid (5 dr ops)Ethanoic acid (glacial) (4cm3)(1)Aspirin tabletPhenolphthalein solutionSodium hydroxide solution (0.1 mol dm-3)95% alcohol4. DIAGRAM4.1 Hirsch move4.2 Melting Point Apparatus5. METHOD8-Shake 2g of 2-hydroxybenzoic acid (salicylic acid) (CARE Irritant) with 4 cm3 of ethanoic anhydride (CARE Corrosive) in a 100 cm3 cone-shaped flask.Add 5 drops of concentrated sulphuric acid (CARE Corrosive) and continue agitating the flask for about 10 minutes. Crystals of Aspirin will appear and soon the whole will form a crystalline mush.Dilute by stirring in 4cm3 of cold glacial ethanoic acid (CARE Corrosive) and cool by placing in a water bath containing crushed ice.Filter off the crystals using a Hirsch funnel (a small funnel for vacuum filtration), washing once with ice cold water to remove residual acid. belongings the stark naked Aspirin in a 100cm3 beaker. Add hot, but not boiling, water until it dissolves. A fold of very pure Aspirin crystals will form cool the flask by surrounding it with cold water.Filter them again and rinse the crystals with the chilled water.The insoluble impurities remain on the filter paper and the filtrate contains the product. Aspirin can be recovered from this solution by evaporation of the recrystallisation.9 Leave the crystals overnight on a watch glass to dry completely. This process is cognise as recrystallisation and is a way of purifying a solid product (Aspirin).Do the recrystallisation process three times and after every recrystallisation remove some sample of Aspirin and store in a test tube to test later.Now do titration of the samples stored after each recrystallisation. Take some of Aspirin for each sample and leave some in the test tube for testing the melting point.For the process of titration, take the Aspirin from each sample into a 50 cm3 conical flask and dissolve it in 5 cm3 of 95% alcohol and add two drops of phenolphthalein solution to it.Titrate the solution in the conical flask with 0.1 mol dm-3 sodium hydroxi de from a burette (CARE Eye protection must be worn).Record the volume needed to produce the first-year tinge of pale pink colour in the indicator. This measure the end-point of the titration.Take a capillary tube and gently press the open end into the big money of Aspirin crystals on the paper so that afewcrystals of Aspirinenter the capillary tube.Tap the closed end of the capillary onto the bench top, so that the Aspirincrystals work their way to the bottom. The Aspirin crystals should be firmly packed, and fill the capillary tube to a depth ofno more than1-2 mm. Insert the capillary tube containing the sample into the melting point apparatus. Record the temperature where the melting point is first observed and when it becomes a liquid completely. This is your melting point range.10Then do the titration of an original tablet of Aspirin available in the market. Then test the melting point of the original tablet of Aspirin by the method set forth above.Compare the melting point which you get from the samples and the original tablet of Aspirin with the one given in the data booklet.6. OBSERVATIONS-When I mixed salicylic acid with ethanoic anhydride, the solution turned milky. When to the solution I added concentrated sulphuric acid, the solution turns colourless and then after agitating for 10 minutes the solution again turns milky white. The beaker is hot and hence we can say that the reaction between concentrated sulphuric acid and the solution (ethanoic anhydride + salicylic acid) is exothermic.When I was doing my melting point I saw that the solid obtained after the first recrystallisation actually turned black before actually getting close to the melting point of the original Aspirin. As the reduce of recrystallisation increased I could see that the melted Aspirin was still white and was getting closer to the melting point of the original Aspirin (135C) as mentioned in the data book.7. DATA COLLECTION AND PROCESSING-7.1 The data of titrations of diff erent recrystallisation samples of Aspirin-7.1.1 Original Aspirin tabletBurette solution (cm3)0.1 mol dm-3 sodium hydroxide solutionIndicatorPhenolphthalein solution running1st interpretation2nd interlingual rendition3rd readingBurette readings (cm3)Final (0.1)44.544.044.044.3Initial (0.1)69.069.069.069.0Volume used (titre) cm3 (0.2)25.025.0I have not used as they are not concordant.I have used these reading for my mean titre.Mean titre (cm3) (0.2)25.0 + 25.0 = 50.050.0 2 = 25.0 (mean titre)Volumetric calculationsVolume of NaOH used = 25.0 cm3.Moles of NaOH n = CV V = 25.0 cm3 = 25.0 1000 = 0.025 dm3 n = 0.1 - 0.025 = 0.0025 molSo, moles of Aspirin will also be equal to 0.0025mol because the reaction ratio between NaOH and Aspirin is 11.Weighed out sample of Aspirin = 0.62 gHow many grams of Aspirin reacted with NaOH?Aspirin = C9H8O4g = n - Mr= 0.0025 - Mr (12.01 - 9) + (1.01 - 8) + (16.00 - 4)= 0.0025 - 180.17= 0.45 g division of Aspirin reacted = (0.45 0.62) - 100= 73%7.1.2 A spirin after 1st recrystallisationBurette solution (cm3)0.1 mol dm-3 sodium hydroxide solutionIndicatorPhenolphthalein solution runnel1st reading2nd reading3rd readingBurette readings (cm3)Final (0.1)3.43.63.73.8Initial (0.1)0.00.00.00.0Volume used (titre) cm3 (0.2)3.63.73.8I have used these reading for my mean titre.Mean titre (cm3) (0.2)3.6 + 3.7 + 3.8 = 11.111.1 3 = 3.7 (mean titre)Volumetric calculationsVolume of NaOH used = 3.7 cm3.Moles of NaOH n = CV V = 3.7 cm3 = 3.7 1000 = 0.0037 dm3 n = 0.1 - 0.0037 = 0.00037 molSo, moles of Aspirin will also be equal to 0.00037mol because the reaction ratio between NaOH and Aspirin is 11.Weighed out sample of Aspirin = 0.30 gHow many grams of Aspirin reacted with NaOH?Aspirin = C9H8O4g = n - Mr= 0.00037 - Mr (12.01 - 9) + (1.01 - 8) + (16.00 - 4)= 0.00037 - 180.17= 0.066 g parting of Aspirin reacted = (0. 066 0.30) - 100= 22%7.1.3 Aspirin after 2nd recrystallisationBurette solution (cm3)0.1 mol dm-3 sodium hydroxide solutionIndicatorPh enolphthalein solutionTrial1st reading2nd reading3rd readingBurette readings (cm3)Final (0.1)12.612.112.112.3Initial (0.1)9.29.29.29.2Volume used (titre) cm3 (0.2)2.92.9I have not used as they are not concordant.I have used these reading for my mean titre.Mean titre (cm3) (0.2)2.9 + 2.9 = 5.85.8 2 = 2.9 (mean titre)Volumetric calculationsVolume of NaOH used = 2.9 cm3.Moles of NaOH n = CV V = 2.9 cm3 = 2.9 1000 = 0.0029 dm3 n = 0.1 - 0.0029 = 0.00029 molSo, moles of Aspirin will also be equal to 0.00029mol because the reaction ratio between NaOH and Aspirin is 11.Weighed out sample of Aspirin = 0.15 gHow many grams of Aspirin reacted with NaOH?Aspirin = C9H8O4g = n - Mr= 0.00029 - Mr (12.01 - 9) + (1.01 - 8) + (16.00 - 4)= 0.00029 - 180.17= 0.052 g percentage of Aspirin reacted = (0. 052 0.15) - 100= 35%7.1.4 Aspirin after 3rd recrystallisationBurette solution (cm3)0.1 mol dm-3 sodium hydroxide solutionIndicatorPhenolphthalein solutionTrial1st reading2nd reading3rd readingBurette readings (cm3)Final (0.1)17.217.617.917.9Initial (0.1)13.113.113.113.1Volume used (titre) cm3 (0.2)I have not used as they are not concordant.4.84.8I have used these reading for my mean titre.Mean titre (cm3) (0.2)4.8 + 4.8 = 9.69.6 2 = 4.8 (mean titre)Volumetric calculationsVolume of NaOH used = 4.8 cm3.Moles of NaOH n = CV V = 4.8 cm3 = 4.8 1000 = 0.0048 dm3 n = 0.1 - 0.0048 = 0.00048 molSo, moles of Aspirin will also be equal to 0.00048mol because the reaction ratio between NaOH and Aspirin is 11.Weighed out sample of Aspirin = 0.15 gHow many grams of Aspirin reacted with NaOH?Aspirin = C9H8O4g = n - Mr= 0.00048 - Mr (12.01 - 9) + (1.01 - 8) + (16.00 - 4)= 0.00048 - 180.17= 0.086 gPercentage of Aspirin reacted = (0. 086 0.15) - 100= 57%7.1.5 Aspirin after 4th recrystallisationBurette solution (cm3)0.1 mol dm-3 sodium hydroxide solutionIndicatorPhenolphthalein solutionTrial1st reading2nd reading3rd readingBurette readings (cm3)Final (0.1)21.320.921.021.1Initial (0.1)16.916.916. 916.9Volume used (titre) cm3 (0.2)4.04.14.2I have used these reading for my mean titre.Mean titre (cm3) (0.2)4.0 + 4.1 + 4.2 = 12.312.3 3 = 4.1 (mean titre)Volumetric calculationsVolume of NaOH used = 4.1 cm3.Moles of NaOH n = CV V = 4.1 cm3 = 4.1 1000 = 0.0041 dm3 n = 0.1 - 0.0041 = 0.00041 mol So, moles of Aspirin will also be equal to 0.00041mol because the reaction ratio between NaOH and Aspirin is 11.Weighed out sample of Aspirin = 0.10 gHow many grams of Aspirin reacted with NaOH?Aspirin = C9H8O4 g = n - Mr= 0.00041 - Mr (12.01 - 9) + (1.01 - 8) + (16.00 - 4)= 0.00041 - 180.17= 0.074 g Percentage of Aspirin reacted = (0. 074 0.10) - 100 = 74%7.2 The data of melting points of different recrystallisation samples of Aspirin-7.2.1 Melting point after first recrystallisationNumber of recrystallisationTemperature (C) ( 0.1C)Original melting point of Aspirin (C)Trial1st reading2nd reading3rd readingAverage1155.0152.5151.9151.7152.0135.02154.1150.0148.5148.2148.9135.03115.2120.912 2.8122.9122.2135.04124.7125.4126.1126.9126.1135.0Original tablet128.0128.8129.2129.9129.3135.07.2.2 Graph showing the difference between melting points of Aspirin which was prepared and recrystallised in lab and melting of Aspirin from the data bookY-axis = temperature (in C)X-axis = number of recrystallisations of aspirin samples prepared in lab and aspirin available in market8. INTERPRETATION OF THE DATAI will now explain the results of melting point and titration. From the results of titrations we can see a trend flowing and how after each recrystallisation the sample gets purer. As the quantity of Aspirin decreased after each recrystallisation, the smokestack of Aspirin in that quantity was more compared to the previous recrystallisation. When compared to the original tablet which we get in the market, I could speculate that the producer has done almost quaternion recrystallisations to get that purity of Aspirin. More pure Aspirin can be obtained if more recrystallisations are done.We could say that the difference in melting point great power be higher because it might contain impurities like unreacted salicylic acid or other by-products of the reaction or decomposition products. We can see that the difference in the melting point is getting less as the number of recrystallisation increase and closer to the melting point of Aspirin published in the data booklet. move on evidence to my theory that the number of recrystallisations increases the purity is my melting point data. From my graph it can be seen clearly that as the number of recrystallisations increase the closer to the melting point of pure aspirin we get in the market.My data shows that the percentage purity of aspirin increased with each recrystallisation process. For example, after the first recrystallisation the percentage purity was only 22%, however when fourth recrystallisation was done the percentage purity was 74% showing a significant increase. This can be seen in the side by side(p ) graph-9. CONCLUSIONIn answer to my research question, How does the process of recrystallisation improve the purity of Aspirin? I have found significantly that the percentage purity increases with each recrystallisation and this is evident in my graph under the heading Interpretation of the data.Recrystallisation is an important technique in organic Chemistry. The general method is to find a solvent that dissolves the product more readily at high temperature than at low temperature, make a hot solution, and allow to crystallise on cooling. The crude product might contain impurities which are insoluble in the solvent impurities which are slightly soluble in the solvent and impurities which dissolve readily in the solvent. The solvent itself has also to be removed or it behaves as an impurity in its own right. It must not leave behind any residue. unrivalled simple way to tell whether an organic compound is pure is to measure its melting (or boiling) point. A pure compound melts sha rply if impurities are present it melts belatedly (over a range of temperature).11The process of recrystallisation in my experiment increased the purity of Aspirin but with a decrease in the quantity produced. The solid will readily dissolve in a larger quantity of solvent the larger the volume of solvent the greater the hurt of product12. This is the reason why after every recrystallisation I lose Aspirin. The process of recrystallisation removes the impurities present and this can be concluded from the fact that the difference between the melting point of the sample and the melting point of Aspirin from data booklet decreases with each recrystallisation.I could conclude that a pharmaceutical company should always have a rest between producing a very pure product, which means many recrystallisation processes and producing enough quantity of the product to make it a profitable industry.10. EVALUATION10.1 Random breakThe apparatus I used had uncertainties like the measuring flask has an uncertainty of 0.5cm3, the burette had an uncertainty of 0.1cm3 and the melting point apparatus also had an uncertainty of 0.1C. This results in errors in my results. The equipment error could be reduced by using equipments with less error. For example, I could use a burette with an error of 0.05 cm3 instead of a burette with error of 0.1 cm3.10.2 Systematic errorIn the process of titration there could a parallax error caused if the reading from the burette is not read at eye-level. So, when taking the reading from the burette, the level of the eye should be same as the level of the meniscus. When we are titrating different samples of recrystallisations the colour of the indicator changes from pale pink to dark and it is difficult to have it off the end-point of the titration process.10.3 Modifications in the method of preparation of Aspirin and its recrystallisationI modified the method to improve it in the following ways After each recrystallisation there was loss of As pirin and the decrease in the mass of Aspirin limited the number of recrystallisations needed to get the most pure form of Aspirin. So, if I doubled the mass of reactants I can get doubled the mass of Aspirin produced and an increase in the number of recrystallisations. When I mixed salicylic acid and ethanoic anhydride solution in concentrated sulphuric acid it is hard to get the formation of a crystalline mush of Aspirin by agitating the flask. Hence, instead I used a magnetic stirrer which gives a uniform stirring and all the chemicals are mixed properly. I found this to be more effective at producing the mush. During the process of recrystallisation a lot of Aspirin is lost. When I used the filter paper, I cut it the same size as the Hirsh funnel. Instead I could have used a bigger filter paper in the funnel so that the impurities do not leak out of the edges of the filter paper and I could get a purer sample of Aspirin. When the Aspirin is left overnight to dry in an evaporatin g dish, there could be many contaminants which would get mixed in the Aspirin and if this is not taken into consideration in pharmaceutical industries then this could lead to serious health problems. Hence, the Aspiring should be covered when left overnight to dry. I could use different methods of purification of Aspirin like thin layer chromatography which is a sensitive and quick way of detecting impurities in an organic product (Aspirin). I could also use spectroscopy which provides a very good method for analyzing an organic compound. By comparing the infra-red spectrum for Aspirin with the spectrum of compound in a database I can check on its purity.11. UNANSWERED QUESTIONSUnfortunately, not all my questions could be answered in this experiment. It would have been interesting in further researching and comparing more brands of Aspirin available in the market, if the producers just recrystallised the sample of Aspirin twice so that they do not lose a lot of their product in the process of recrystallisation or the producers actually tried to produce a pure sample of Aspirin ignoring the decrease in yield after each recrystallisation and considering the fact that this can affect the health of humans.When an organic compound has been made it needs to be purified, particularly if it is apharmaceutical chemical. This is because most organic reactions produce by-products but, even if the reaction is a clean one, the purity standards for many products are so stringent that small amounts of other compounds have to be removed. In particular the catalyst used in this reaction is concentrated sulphuric acid and must all be removed.