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Dec 6, 2023

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Introduction: Although aspirin is used extensively worldwide, willow bark was utilised for fever and pain relief prior to the availability of aspirin. Salicylic acid, a byproduct of acetylsalicylic acid (aspirin), is found in plants such as willow bark. Aspirin and salicylic acid are members of the same salicylate family. It is reported that Hoffman's father inspired him to create a medication free of sodium salicylate2 unpleasant side effects, which led to the creation of aspirin. Hoffman was able to synthesise acetylsalicylic acid as a result, and in 18992 it was sold under the name aspirin. Aspirin is presently used to treat fever, inflammation, pain, and to reduce the risk of heart attacks, heart disorders, and some types of cancer. The multistep synthesis procedure for acetylsalicylic acid preparation was completed. In multistep processes, the compounds are converted into products in one reaction, which are then used as reactants to create a new product in reaction two. Until the intended outcome is obtained, this process is repeated. In this lab, acetylsalicylic acid was the final result of a multistep synthesis that took place in two reactions. This lab aims to synthesise acetylsalicylic acid by means of a multistep reaction that must be successfully completed. This substance is well-known for being an ingredient in medications like aspirin, which is frequently used as an anti-inflammatory and to treat and relieve mild aches and pains. The three-week duration of the trial was observed. Using an aqueous base, the methyl salicylate was first broken down. The initial byproduct of this hydrolysis is the sodium salt of salicylic acid, aside from methanol and water. The addition of sulfuric acid to the reaction mixture caused the sodium salt to change into a free acid. Methanol and salicylic acid are the process's end organic compounds. The following figure depicts this response; The second part of this experiment is the acetylation of ASA to make acetylsalicylic acid. This requires an acid catalysed interaction between salicylic acid's phenolic OH and the acetylating agent, acetic anhydride, to produce the ester, acetylsalicylic acid. The phenol functions as a nucleophile in this reaction, starting a substitution process at one of the carbonyl groups in the anhydride. Because acetic anhydride is highly reactive, refluxing it only requires a gentle soak in

warm water. Heating is not necessary to initiate the reaction. The catalyst in this process is sulfuric acid. Water is added to remove any surplus acetic anhydride when the reaction is finished. The third week is dedicated to completing the required analysis and purification. Several methods will be employed in the product analysis. Using a range of methods, the products will be purified and analysed during the third week of this lab. One crucial and often utilised method in chemistry labs is vacuum filtration. Vacuum filtering is accomplished by inserting a Büchner funnel into the top of the vacuum flask and attaching the side arm to the vacuum tap via the thick tube. In order to prevent crystals from leaking through and losing product in the vacuum flask during the filtration process, a filter paper should also be placed within the Büchner funnel. The crystals are separated from the mother liquor by using this procedure, which is applied after the solution is put into the Buchner funnel. After that, there will still be some mother liquor residue in the crystals, so it's crucial to wash them in cold distilled water to make sure all of the mother liquor is removed and the final product contains fewer contaminants. After vacuum filtration, it is crucial to let the crystals dry. If the product is measured early, the weight will contain some water, resulting in an inaccurate and less pure yield. In this lab, we employ the reflux technique to induce an organic reaction. Refluxing refers to setting up the reaction at a steady temperature without allowing any solvents or vapours to escape into space. By comparing the measured melting point range to a value found in the literature, the melting point test and analysis will be the first test utilised to determine the substance's purity. A small sample of the solid material is heated gradually (at a rate of 1°C per minute) in order to ascertain the melting point. The second test will be the ferric chloride test, which will be run on the starting materials, intermediates, products, and some related chemicals. The ferric chloride test is a method used to ascertain the presence of phenol, enols, a particular carboxylic acid, or a specific chemical in a solution by adding ferric chloride (FeCl3) to it. If it does, you will be able to determine the identification and purity of the specified compounds thanks to a distinctive colour shift. Thin layer chromatography (TLC), a two-phase technique for detecting and isolating mixtures of substances, is another way to assess the purity of the solution. The chemical is absorbed in the first phase, referred to as the "stationary phase," and is assisted in moving along the stationary phase by the second phase, referred to as the "mobile phase." The produced acetylsalicylic acid and the other reactants or intermediates will be chromatographed using TLC. After being dissolved in an appropriate solvent, the methyl salicylate samples will be spotted onto the plate's surface at one end. The spots will be allowed to dry before the plate is immersed in a developing tank filled with a small amount of developing solvent. The components will be moved up the plate by capillary action as the solvent flows along the length of the plate. Another method for assessing a compound's purity is infrared spectroscopy, which gauges energy absorbance. In order to do this, absorbances are combined to produce a fingerprint that can be used to identify the molecule. Purified and crude acetylsalicylic acid will be

examined in this experiment, and the purity will be determined by comparing the reactant spectra. One method used to separate and identify combinations of certain analgesics is thin layer chromatography. There are two phases: the mobile phase, which is the solvent system and moves along the plate via capillary action, and the solid phase, which in this case is silica. The polarity and structural similarity will draw each other and prevent the compounds from moving across the plate as quickly as the non-polar compounds would. Each compound will have a different length for this. The figure known as the retention factor indicates how far the chemicals have moved across the chromatography plate in the solvent. The retention factor can be computed using the following equation: Rf is equal to the product of the substance's mm journey and the solvent's mm travel. This investigation also included infrared analysis. One method for measuring the amount of energy absorbed by the molecule is infrared spectroscopy. Experimental First week After reweighing a 250 mL round-bottom flask, 5.0 g of methyl salicylate and 50 mL of a 20% NaOH solution were added. After that, a reflux condenser was fastened to the flask, a little oil was applied to the glass joints, and a few boiling chips were added to the reaction mixture. In order to ensure that the reflux level is in the centre of the condenser, the solution was heated to its boiling point for 20 minutes while carefully monitoring the pace of heating. The mixture was allowed to cool for five to ten minutes after twenty minutes. Following a vacuum filtration, the resultant material was weighed and stored aside for melting point analysis. The crude Salicylic acid was recrystallized from water. A small sample of crude salicylic acid was kept for TLC analysis while the rest of the acid was dissolved in a 250 mL beaker with very little water added. The mixture is then heated to a boil. Once boiling, the beaker is covered with a watch glass and permitted to cool and crystallise on its own. To encourage crystallisation, the beaker was submerged in an ice bath after the process began. The beaker was taken out of the ice bath after ten minutes, and the crystals were collected using vacuum filtration. Weighing was done on the pure salicylic acid generated in the first week of the trial. Second week The salicylic acid generated in week one was weighed during the second week of the experiment, and the melting points of the crude and refined salicylic acid were measured and noted. A 400 mL beaker filled with three to four boiling chips and around 100 mL of distilled water was heated to 45 to 50 °C in order to provide a warm water bath for the aspirin production. Salicylic acid weighing 3.0 g was added to a 100 mL dry and clean beaker. The salicylic acid beaker was filled with 5.0 mL of acetic anhydride after it had been placed into a 10 mL graduated cylinder.

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To guarantee adequate mixing, 5 drops of strong sulfuric acid were cautiously added to the beaker containing salicylic acid and acetic anhydride, and the mixture was agitated with a rod. In the water bath, the mixture was heated while being stirred until the solid was dissolved. After that, the mixture was heated for five to fifteen minutes. After being taken out of the water bath, the beaker was allowed to cool to room temperature without being touched. It was noted that acetylsalicylic acid crystals were beginning to form. The mixture was placed on ice until it thickened into a semi-solid mass after the solution and beaker had cooled. Following crystallisation, the beaker was filled with 50 millilitres of ice-cold distilled water. The crude aspirin crystals were then vacuum-filtered and cleaned with tiny volumes of chilled distilled water. After five minutes of suction, the crystals were gently fluffed using a glass stirring rod, being careful not to tear the filter paper. The crystals were removed from the filter paper and put into a dry, clean weight dish once the vacuum filtration process was finished. They were then weighed using a top loading balance. To finish TCL and IR analysis, chemical tests, and a melting point determination test, a tiny sample of impure crystals was set aside. Re- crystallization of the crude aspirin required little hot solvent. In a 250 mL beaker, the crystals were dissolved with 20 mL of water, 5 mL at a time, until the aspirin was entirely dissolved. It was noted how much hot water was used. After the beaker was placed in an ice bath, it was covered with a watch glass and left to cool to room temperature without being disturbed. Following a brief wash with ice-cold solvent, the aspirin-purified crystals were vacuum-filtered. When the crystals were totally dry, they were transferred to a fresh, dry 50 mL beaker and kept there until the next week. Third week In week three, the purified acetylsalicylic acid from the previous lab was weighed and subjected to a melting point examination. The TLC plate was very faintly marked with a pencil to mark the start of the test. The line was placed 2 cm from the bottom of one end of the plate. Both the generated acetylsalicylic acid and the standards were spotted at this point. This information was captured and a map showing the spots' application sequence was made. There are seven lanes created: salicylic acid, acetylsalicylic acid, pure methyl salicylate, crude acetylsalicylic acid, purified salicylic acid, crude salicylic acid, and purified acetylsalicylic acid. Four microliters of solution were drawn up using the capillary at each station. To empty the capillary into the silica gel, the plate's surface was gently wiped, letting the material dry in between dabbing strokes. Using the same capillary tube, the same component was sampled and spotted three times. After spotting all of the normal chemicals, the plate was left to dry for two to three minutes, during which time acetylsalicylic was formed. When the solvent had moved about 80% of the plate's distance, the plate was carefully taken out of the tank and the solvent front was quickly traced onto the plate with a pencil before the solvent evaporated. The bottom end of the plate containing the spotted samples touched the solvent. After that, the plate was placed in the fume hood and given ten minutes to dry. Any visible areas on the plate were traced with a pencil after they had dried. The fluorescent dots on the plate were highlighted with a pencil after it was brought into a dark room and exposed to UV light. Both the solvent's travel distance and the distance from the

start line to each spot's leading edge were measured. Each compound's colour was observed and recorded, the information was recorded on a data sheet and the plates were put into the fume hoods. Seven tiny test tubes, labelled #1 through #7, were acquired for the ferric chloride test, and each test tube received 0.5 mL of methanolic ferric chloride solution. Each test tube was filled with a few drops of a separate sample (pure and crude salicylic acid and acetylsalicylic acid, pure methyl salicylate, salicylic acid, and acetylsalicylic acid). The liquids were swirled together, and any colour changes were recorded. Following testing, the test tubes were properly cleaned, and the test solutions were disposed of in the appropriate waste containers. Appendix B-3 included instructions on how to operate the spectrometer for Infrared Spectroscopy. It is necessary to get the spectra of acetylsalicylic acid and salicylic acid, both pure and crude. Results: Compound Formula Molecular weight (g/mol) Melting Point( º C) Boiling point( º C) Density (g/cm 3 ) Methyl Salicylate C8H8O3 152.148 -8.50 220 1.17 Sodium Hydroxide NaOH 39.997 323.00 1388 2.13 Sulphuric acid H2SO4 98.079 10 337 1.83 Water H 2 O 18.015 0 100 0.9998395

Methanol CH 3 OH 32.04 -97.6 64.7 0.792 Acetic anhydride C4H6O3 102.09 -73.1 139.5 1.082 Salicylic acid C7H6O3 138.121 158.60 211 1.44 Table 2: Physical properties of products Compound Formula Molecular weight (g/mol) Melting Point( º C) Boiling point( º C) Density (g/cm 3 ) Salicylic acid C7H6O3 138.121 158.60 211 1.44 Sodium Bisulfate NaHSO 4 120.06 58.50 315 2.74 Acetyl salicylic acid C9H8O4 180.158 135 140 1.40 Methanol CH 3 OH 32.04 -97.6 64.7 0.792 Acetic Acid CH 3 COOH 60.052 16.6 118 1.05

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Table 3: Data provided with melting point ranges and concentrations created of crude and purified salicylic acid (SA) and acetylsalicylic acid (ASA) Compound weight Melting point range Crude Salicylic acid 4.5 147-158 Pure Salicylic acid 3.7 157-161 Crude Acetylsalicylic acid 4.4 125-135 Pure Acetylsalicylic acid 2.8 131-135 Table 4: Data results for Ferric chloride Compound Observations Standard Methyl Salicylate Blackish purple tint; Positive Standard Salicylic Acid Blackish purplish tint; Positive Standard Acetylsalicylic Acid Yellowish golden tint; Negative Crude Salicylic Acid Blackish purple tint; Positive

Pure Salicylic Acid Blackish purplish tint; Positive Crude Acetylsalicylic Acid Golden brownish tint, Negative Pure Acetylsalicylic Acid Light Golden brownish tint, Positive Figure 1. Ferric Chloride test results Table 5: Data results for TLC (Thin-layer chromatography ) Compound Distance Travelled Between Start Line (cm)

Standard Methyl Salicylate 5.2 Standard Salicylic Acid 5.1 Standard Acetylsalicylic Acid 5.1 Crude Salicylic Acid 5.1 Pure Salicylic Acid 5.1 Crude Acetylsalicylic Acid 4.8 Pure Acetylsalicylic Acid 4.75 Solvent Front 6.0 Sample calculation of Rf value for standard methyl salicylate: ? ? = ?𝑖?????? ?????𝑙?? ?𝑦 ??𝑙??? ?𝑖?????? ?????𝑙?? ?𝑦 ??𝑙????

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= 5.2 6.0 = 0. 8667 Table 6. The Rf Values of the Compounds Compound Retention Factor Standard MS 0.867 Standard SA 0.850 Standard ASA 0.850 Crude SA 0.850

Pure SA 0.850 Crude ASA 0.800 Pure ASA 0.800 Compound Mass Molar mass (g/mol) Moles(mol) Density(g/cm 3 ) Methyl Salicylate 5g 152.15 0.033 1.17 Sodium Hydroxide 50mL 39.99 2.66 2.13 Sulfuric Acid 250mL 98.08 4.693 1.83 Salicylic Acid 3g 138.12 0.0 1.44

Acetic Anhydride 5mL 102.09 0.053 1.08 Sulfuric acid 5 drops 98.09 1.83 Calculations: a. Percentage yield for pure SA 𝑀𝑜?? ?𝐴 = 5𝑔 152.15 = 0. 03286 ?𝑜?? ? ℎ ?𝑜???𝑖?𝑎? 𝑦𝑖??? = 03285 × 138. 121 ? / ?𝑜? = 4. 5 ??𝑎?? % 𝑦𝑖??? = ?????𝑙𝑦𝑖?𝑙? ?ℎ?????𝑖??𝑙 𝑦𝑖?𝑙? × 100% = 3.7𝑔 4.5𝑔 × 100 % = 0. 82= 82% B 𝑀𝑜?? A ?𝐴 = 3𝑔 138.12 = 0. 02172 ?𝑜?? ? ℎ ?𝑜???𝑖?𝑎? 𝑦𝑖??? = 02172 × 180.16 ? / ?𝑜? = 3.9 ??𝑎??

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% 𝑦𝑖??? = ?????𝑙𝑦𝑖?𝑙? ?ℎ?????𝑖??𝑙 𝑦𝑖?𝑙? × 100% = 2.8𝑔 3.9𝑔 × 100 % = 0. 7179= 71.79% Figure 1: Infrared Spectroscopy analysis of pure acetylsalicylic acid (ASA) 0 10 20 30 40 50 60 70 80 90 100 500 1000 1500 2000 2500 3000 3500 4000 %trasmittance wave number Graph showing pure acetylsalicylic acid IR Compound Theoretical Yield Percentage Yield Pure Salicylic Acid 4.5 g 82% Pure Acetylsalicylic Acid 3.9 g 71.79%

Figure 2: Infrared Spectroscopy analysis of pure salicylic acid (SA) Discussion: We finished the multistep synthesis of acetylsalicylic acid in this lab and carried out a number of tests to ascertain the purity of the chemicals that were created. The ferric chloride test, melting point determination, thin layer chromatography (TLC), and infrared spectroscopy analysis were the tests that were carried out. The percent yield was evaluated using. the % yield= ?????𝑙 𝑦?𝑖𝑙? ?ℎ??????𝑖??𝑙 𝑦?𝑖𝑙? × 100% pure salicylic was weigh out to be 3.7g and the % 𝑦𝑖??? was calculated to be 82%. pure acetylsalicylic acid weigh 2.8g and its percentage yield is 71.79%. We can see that none of the percentage yields are 100%, and when we compare the yield percentages of SA and ASA, the value dropped by 10.21%. This is probably because of a variety of mistakes, such as mass loss from vacuum filtration, product loss during crystallisation, or during the substance's transfer to different vessels. Melting point analysis was the first test carried out. The temperature at which a substance turns from solid to liquid is known as its melting point; the range of temperatures between the point at which the crystals first start to liquefy and the point at which the sample becomes liquid is known as its melting point range. The majority of pure chemicals melt between one and two degrees Celsius. The melting point of pure salicylic 0 20 40 60 80 100 120 500 1000 1500 2000 2500 3000 3500 4000 wave number Graph showing pure salicylic acid IR

acid is 157–161ºC, as shown in table 3 above, however table 1 shows that the actual value is 158.60ºC. The 0°C–2°C difference indicates the purity of the experimental pure SA, which may be the result of various minute contaminants added during SA synthesis. Table 3 shows that pure acetylsalicylic acid has a melting point range of 131ºC to 135ºC, while Table 2 displays the literature value of 135ºC. The experimental pure ASA is pure, as indicated by the slight temperature difference. Additionally noted were the salicylic acid and acetyl salicylic acid crude melting point ranges. Table 3 shows that the crude salicylic melting point ranges from 147ºC to 158°C, with a 3°C–16°C variation between the values found in the literature and the actual values. The measured melting point range of crude acetylsalicylic acid was found to be 125ºC–135ºC, with a difference of 5°C– 15°C between the observed and literature values. Both crude SA and ASA are regarded as impure because of the significant temperature difference, which suggests that both contain impurities. The TLC test is the one that is performed next. Figure 2 shows that pure salicylic acid and crude salicylic acid went the same distance and, as a result, had the same retention factor, 0.850, proving their purity. Figure 2 further demonstrates that the retention factors of 0.800 were observed for both crude and pure acetyl salicylic acid, indicating that they travelled the same distances. The ferric chloride test was another procedure used to assess the products' purity. Seven compounds were tested for the presence of phenols using the ferric chloride test: Standard MS, Standard SA, Standard ASA, Crude SA, Pure SA, Crude ASA, and Pure ASA. The sample turned purple upon the addition of ferric chloride to standard MS, standard SA, crude SA, and pure SA, signifying the presence of phenol. The goods' purity was also assessed using the ferric chloride test, which examined the following: Standard MS, Standard SA, Standard ASA, Crude SA, Pure SA, Crude ASA, and Pure ASA .Finding out if the compounds in question contain phenols is the purpose of this test. The mixture will turn a dark purple tint if it includes phenol groups. The four test tubes—standard MS, standard SA, crude SA, and pure SA—that took on a blackish purple hue. This indicates the presence of a phenol group in each of these four compounds. The golden brownish hue of the other three test tubes—standard ASA, crude ASA, and pure ASA—suggested the absence of phenol groups, indicating the purity of the acetylsalicylic acid prepared in the laboratory. The last test used to assess the chemicals' purity was IR analysis. This test makes use of the fact that various compounds absorb different infrared wavelengths depending on their bonds and functional groups. Pure salicylic acid and acetylsalicylic acid's IR analysis graphs are quite similar, and the functional groups that are shown in the Ketone, carboxylic acid, and ester groups made up the graphs. The visual similarity of the two plots suggests that the salicylic acid that was purified was pure. Several factors can lead to errors in this lab, such as acetic anhydride hydrolyzing quickly in the presence of water; if there is leftover water in the beaker used to obtain this substance, some reactant may be lost; some product may have lost mass during recrystallization; if the rate of heating was too fast during the melting point determination, the melting point would be lower; transferring the compounds to different beakers can also lead to errors in this lab;

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some product may be lost in the process, and it's crucial to scrape off the filter paper properly to obtain the maximum yield. Conclusion: Chemistry and medicine have both advanced as a result of the synthesis of painkillers. Calculating the yield allowed one to determine the accuracy of the process utilised in the salicylate production process, which involved the saponification of methyl salicylate. The computed yield came to 82%. Salicylic acid was used to create ASA, which yielded a 71.79% yield. Both items underwent an IR test and a TLC plate test to determine their purity. The experiment can be deemed successful in the end because the experimental pure salicylic acid and pure acetylsalicylic acid yield percentages of 82% and 71.79%, respectively. Different experimental mistakes are the cause of the percentage yields not reaching 100, and product loss caused the yield to fall from 82% to 71.79%. Acetylsalicylic acid and salicylic acid used in the experiment were found to be pure by the melting point range test; the compound's purity was also successfully ascertained by the other tests. Reference: Vlot, A. C., Dempsey, D. M. A., & Klessig, D. F. (2009). Salicylic acid, a multifaceted hormone to combat disease. Annual review of phytopathology, 47, 177-206. CHY 142 | Department of Biology and Chemistry. (2021). Retrieved from https://courses.ryerson.ca/d2l/le/content/530499/viewContent/3821454/View