Synthesis of Aspirin: Experimental Results and Analysis, Summaries of Organic Chemistry

Download Synthesis of Aspirin: Experimental Results and Analysis and more Summaries Organic Chemistry in PDF only on Docsity! N. Wulff, Synthesis of aspirin Synthesis of Aspirin Abstract The purpose of conducting this experiment was to synthesize aspirin by performing a reaction between salicylic acid and acetic anhydride with a phosphoric acid catalyst. This was carried out using a non-microwave method which utilized a hot water bath set to 50°C. This process yielded 0.084g of product, though, the calculated theoretical yield was 0.2748g, therefore, the percent yield was 31%. Four tests were conducted on the product, these being a TLC plate, a ferric chloride test, a melting point test, and an IR spectrum test. The TLC plate test showed a retention factor of 0.95 for salicylic acid and 0.82 for the product. The ferric chloride test showed no phenol presence in either water or the aspirin, though showed a positive phenol presence in the salicylic acid by turning the solution a dark purple from being clear originally. The experimental melting point readings showed salicylic acid having an approximate melting point of 175°C and the aspirin product having a melting point of approximately 130°C. Reading the IR spectrum data, there are peaks in the data which prove the existence of a carbonyl group, hydroxyl group, and an aromatic group in the sample. Introduction The reaction mechanism above shows the reaction between salicylic acid (left) and acetic anhydride (middle) in the presence of phosphoric acid (above reaction arrow) to produce analyzed. Lastly, workstations were cleaned using acetone and all glassware was discarded or cleaned accordingly (Cerny K, Schwartz M, Katz C 117-125). Results Table 1 shows the materials used as well as their properties. Table 2 shows the results of the ferric chloride test. Table 3 shows the experimental melting points compared to the known melting points of the substances. Figure 1 is a copy of the IR spectrum recorded and interpreted. Figure 2 is a TLC plate made using the Rf values of the tested substances. Figure 3 is a visual representation of the ferric chloride test results. Table 1: Properties of Materials Used Table 1: Materials Substance Structure Mole Weight (g/mole) Density (g/mL) Melting Point (°C) Boiling Point (°C) Salicylic Acid 138.122 1.44 158 211 Acetic Anhydride 102.089 1.08 -73.4 139 Acetylsalicyli c acid 180.159 1.4 135 140 Table 2: Results of Ferric Chloride Test Table 2: Ferric Chloride Results Water No change after adding the indicator (negative) Salicylic Acid Changed from clear to dark purple (positive) Product No change after adding the indicator (negative) Table 3: Melting Points Table 3: Melting Points Substance Known MP (°C) Experimental MP (°C) Salicylic Acid 158 175 Acetylsalicylic Acid 136 130 Figure 1: Infrared Spectrum of Product Figure 2: TLC Plate Figure 3: Ferric Chloride Visual Results Sample Calculations Theoretical Yield: 0.2107 g SA× 1 mole SA × 1 mole Asp × 180.159 g Asp =0.2748 g Asp 138.122 g SA 1 mole SA 1 mole Asp Percent Yield: acid. Lastly, the infrared spectroscopy proved a change in the structure of the product as there was a large change in the broad-band between 2300 and 3300 cm-1. The percent yield of this experiment was only 31%, though this was heavily due to error which can be avoided. Post Lab Questions 1. The purpose of using concentrated phosphoric acid was to act as a catalyst. In this reaction, it is used to protonate the reactants, meaning to add protons (H+), which allows the reaction to happen at a faster rate. It is not required to undergo the reaction, though it helps in reducing the time needed for the reaction to reach completion. 2. Using 250 mg of salicylic acid and an excess of acetic anhydride, the theoretical yield would be 326 mg acetylsalicylic acid. This was determined by multiplying the mass of salicylic acid, as it is the limiting reagent, by the molar mass of acetylsalicylic acid because the reaction is 1:1 (Sample calculation can be found in the results section above). 3. According to the lab manual, each aspirin tablet which contains 5-grains of aspirin is usually compounded of approximately 0.32g of acetylsalicylic acid or 320 mg. References Ashenhurst, J. (n.d.). Conversion of carboxylic acids to esters using acid and alcohols (Fischer Esterification). Retrieved from https://www.masterorganicchemistry.com/reaction- guide/conversion-of-carboxylic-acids-to-esters-using-acid-and-alcohols-fischer- esterification/ Cerny K, Schwartz M, Katz C. (2016). Laboratory Manual for Organic Chemistry. Dubuque, IA: Kendall Hunt Publishing Company. Trivedi MK, Branton A, Trivedi D, Shettigar H, Bairwa K, et al. (2015) Fourier Transform Infrared and Ultraviolet-Visible Spectroscopic Characterization of Biofield Treated Salicylic Acid and Sparfloxacin. Nat Prod Chem Res 3:186. doi:10.4172/2329- 6836.1000186