Synthesis of Aspirin Lab Report

The Synthesis andAnalysis of Aspirin Acetylsalicylic acid is the chemical name for aspirin, the ubiquitous pain reliever. One of the compounds used in the synthesis of aspirin is salicylic acid, which is itself a pain reliever that was known to many ancient cultures, including the Native Americans who extracted it from willow tree bark. Salicylic acid is extremely bitter tasting, and frequent use can cause severe stomach irritation. The search for a milder form of this pain reliever led to the successful synthesis of acetylsalicylic acid by the German chemist Felix Hoffmann in 1893. Your two primary objectives in this experiment will be to synthesize and analyze aspirin. There is more than one way to synthesize aspirin; in this experiment, you will react acetic anhydride with salicylic acid in the presence of phosphoric acid (which acts as a catalyst). The reaction equation is shown below. HO HO O O OH + Salicylic acid H3C O O H 3P O CH3 Acetic anhydride 4 O O (a q ) CH3  O O Acetylsalicylic acid + H3C OH Acetic acid You will conduct two tests of your synthesis to verify that you did indeed make aspirin, and to determine its relative purity. First, you will measure the melting temperature of a sample of your product, using a Melt Station. Second, you will use a Spectrophotometer to test the absorbance of salicylic acid impurity in your aspirin sample after it has been complexed with Fe3+ from iron (III) nitrate solution. OBJECTIVES In this experiment, you will     Synthesize a sample of acetylsalicylic acid (aspirin). Calculate the percent yield of your synthesis. Measure the melting temperature of your aspirin sample. Conduct a spectrophotometric analysis of your aspirin sample. Organic Chemistry with Vernier © Vernier Software & Technology 1 Swirl the mixture. Fe(NO3)3 distilled water 100 mL volumetric flask 250 mL volumetric flask PROCEDURE Part I Synthesize Aspirin 1. Obtain and wear goggles. Stir the mixture occasionally during heating. use a sparingly small amount of distilled water to rinse down any bits of solid that may be on the inner walls of the flask. 3. If necessary.MATERIALS Part I Synthesis Materials 50 mL Erlenmeyer flask two 10 mL graduated cylinders 25 mL graduated cylinder 250 mL beaker Büchner funnel. and filter paper spoon. Hold and partially submerge the 50 mL flask and contents in the water bath. Conduct this reaction in a fume hood. filter. You are now ready to begin the synthesis of aspirin. spatula. 4. Add 2 mL of distilled water about 10 minutes into the heating. a. denatured 0. Add 5. b. 2 Organics Chemistry with Vernier .0 g of salicylic acid into a 50 mL Erlenmeyer flask. 2.025 M iron (III) nitrate solution. CAUTION: Handle the phosphoric acid and acetic anhydride with care. one end closed aspirin crystals (from Part I) tissues (preferably lint-free) mortar and pestle (optional) Part III Spectrophotometric Absorbance LabQuest or computer interface LabQuest App or Logger Pro SpectroVis Plus spectrophotometer 50 mL graduated cylinder plastic cuvette with lid 250 mL beaker 100 mL beaker salicylic acid aspirin crystals (from Part I) ethanol. Protect your arms and hands by wearing a long-sleeve lab coat and gloves. or until the mixture ceases releasing vapors. Both substances can cause painful burns if they come in contact with the skin. Prepare a 70–80°C hot-water bath using a 250 mL beaker on a hot plate.0 mL of acetic anhydride and 5 drops of 85% phosphoric acid solution. Measure out 2. Heat the mixture in the hot-water bath for 15 minutes. or rubber policeman ice bath hot plate plastic Beral pipet or eyedropper solid salicylic acid 85% phosphoric acid solution. Monitor the water temperature using a Temperature Probe or thermometer. H3PO4 liquid acetic anhydride distilled water cold distilled water balance Temperature Probe or thermometer watch glass Part II Melting Temperature LabQuest or computer interface LabQuest App or Logger Pro Vernier Melt Station glass capillary tubes. c. Part II Test the Melting Temperature of an Aspirin Sample 8.2 g) of your synthesized aspirin and place it in a small pile in the mortar. Start data collection. Determine the mass of your dry aspirin sample and record in the data table. turn the suction back on. 6. Carefully insert the capillary tube of solid into one of the sample holders of the Melt Station. Transfer the contents of the flask to a Büchner funnel assembly. Organic Chemistry with Vernier 3 . Be sure to weigh and record the mass of the filter paper to the nearest 0. To do this: a. c. 9. As directed by your instructor. Weigh the dried recrystallized product on the filter paper and record the mass to 0. then choose New from the File menu. Filter the mixture with vacuum suction. carefully remove the flask from the hot plate and add 20 mL of distilled water. Start the data-collection program. crystals of aspirin should form in the flask. or let them air dry until the next lab period. Gently transfer the filter paper with your product onto the watch glass to air dry. Pack a capillary tube 3–4 mm (~1/8 inch) deep with your aspirin sample by inserting the open end into the small pile of aspirin. Use a mortar and pestle to pulverize a small amount (about 0. Check the control knob on the Melt Station to confirm that it is in the Off position. Don’t worry if the heating rate is a bit too rapid and the sample melts too quickly. b. c. The red light will turn on indicating active heating. 7. Tap the closed end of the capillary tube on the table top to compress the sample into the closed end.01 g. Allow the mixture to cool to near room temperature. distilled water. b. When you are confident that the reaction has reached completion (no vapors appearing). Now you will wash the synthesized aspirin: a. you will want to observe the melting process and make a rough estimate of the melting temperature of your aspirin sample. You are now set up to take melting temperature data for up to 20 minutes. In the first trial. 11. either direct a gentle stream of air (low flow) to help dry the solid. Prepare a sample for melting: a. Next you will crystallize the aspirin: a. distilled water twice more in this manner. d.The Synthesis and Analysis of Aspirin 5. d. 12. Connect the Melt Station sensor cable to LabQuest or to a computer interface.01 g before filtering the solid. b. A small amount of the solid will be pushed up into the tube. Connect the Melt Station power supply to a powered electrical outlet. 10. On the Melt Station. Set up a vacuum filtration using a Büchner funnel. Wash the crystals with cold. After about 15 seconds. Transfer the flask to an ice bath for about five minutes. e. turn off the suction and wash the crystals with 5 mL of cold. turn the control knob to a setting of 220ºC. As the mixture cools. When most of the liquid has been drawn through the funnel. f. b. e. You will mix iron (III) nitrate with salicylic acid in your aspirin sample to complex the salicylic acid. click Mark again. stop data collection. Start data collection. Swirl the beaker to dissolve the solid. Follow Steps 16–21 to prepare a set of salicylic acid standard solutions and conduct testing to develop your own Beer’s law plot of the standards. of the salicylic acid into acetylsalicylic acid. 15. Now that you have a rough idea of the melting temperature. to determine the melting temperature of the sample: a. You can use this information to calculate the purity of your aspirin sample. Store the run by tapping the File Cabinet icon in LabQuest. Part III Test the Spectrophotometric Absorbance of an Aspirin Sample Your synthesis converted most. turn the control knob to the Fan/Cooling setting to get ready for the next trial. Record the melting temperature range in your data table. When the entire solid has completely melted. When the temperature is within approximately 10ºC of the lowest possible melting temperature of your sample. click Mark again. When you have determined the approximate melting temperature range for the sample. When you are finished with this step. stop data collection. Discard the capillary tube and sample as directed by your instructor. but not all. g. to the nearest 0. When the solid begins to melt. which is a bluish-purple color. click Mark to mark the temperature on your graph. The blue light will turn on indicating that the fan is cooling the Melt Station. click Mark to mark the temperature on your graph (or press the D key on the computer or the OK button on LabQuest). 4 Organics Chemistry with Vernier . 14. 13. c. turn the control knob to the Rapid Heat setting. The two values marked on your graph describe the estimated melting temperature range of your substance. You will analyze several samples to determine the amount of salicylic acid impurity in your synthesized aspirin. Mix the solution. When the entire solid has completely melted. On the Melt Station. d. turn the control knob to a temperature setting corresponding to your expected melting temperature. turn the control knob on the Melt Station to Off. Discard the capillary tube and sample as directed by your instructor. At the end of your testing. a more accurate determination of the melting temperature can be made. Carefully observe the temperature vs. 16. Add 150 mL of distilled water to the beaker. Measure out about 0. When the solid begins to melt.c. c. Quantitatively prepare the stock salicylic acid solution. On the Melt Station. b. The two values marked on your graph describe the estimated melting temperature range of your substance. Store the run. e. a. Carefully observe your sample. Transfer the salicylic acid to a 250 mL beaker and add 10 mL of ethanol. e. or choosing Store Latest Run from the Experiment menu in Logger Pro. d. b.20 g of salicylic acid. Carefully observe your sample.001 g. time graph. Use a previously prepared sample in a capillary tube. On the Melt Station. Record the mass. Repeat Step 13 until you have determined the melting temperature range of your aspirin. turn the control knob to the Fan/Cooling setting to get ready for the next trial. as described in Step 8. f. Steps 22–25 will guide you through the set up and testing of your aspirin sample. Thoroughly rinse the beaker with several portions of distilled water. 20. fill a cuvette 3/4 full with 0. b. to fill the flask to the 250 mL mark. quantitatively transfer 10.0 18. To prepare 100. When the warmup period is complete.0 8. and then fill it 3/4 full. a.0 4. b. and transfer the rinse water to the volumetric flask.The Synthesis and Analysis of Aspirin d. Calculate the precise molar concentration of your stock solution and record it in your data table. The wavelength of maximum absorbance ( max) is automatically identified. Prepare the remaining four salicylic acid standard solutions according to the table below. Prepare five standard solutions of varying concentrations of salicylic acid.0 mL of the stock salicylic acid solution you prepared in Step 16 to a 100 mL volumetric flask. diluting the standard solution in the 100 mL flask with distilled water. c. rinse the cuvette twice with ~1 mL amounts. b.025 M Fe(NO3)3 solution. Trial Standard salicylic acid solution from Step 17 a–b (mL) Water (mL) 1 2 3 4 5 10.0 6. Mix the solution thoroughly. Start data collection. Calibrate the Spectrophotometer. Add 0. Determine the optimal wavelength for creating the standard curve and set up the mode of data collection. Choose Calibrate from the Sensors menu of LabQuest or the Experiment menu of Logger Pro.0 0 2. Place the blank cuvette in the Spectrophotometer. A full spectrum graph of the solution will be displayed. Start the data-collection program. Calculate the precise molar concentrations of the five standard solutions in the table above and record them in your data table. 17.0 4. Quantitatively transfer the solution from the beaker to a 250 mL volumetric flask. then choose New from the File menu. 19. Wipe the outside with a tissue and place it in the Spectrophotometer.0 mL of your standard solution (the solution you will use for Trial 1). Disconnect the Melt Station and connect the Spectrophotometer to the USB port of LabQuest or a computer. select Finish Calibration. Mix thoroughly. Empty the Fe(NO3)3 solution from the blank cuvette. Organic Chemistry with Vernier 5 . Using the solution in the 100 mL volumetric flask of salicylic acid (Trial 1).0 8. a.0 2. a. as needed. b.0 6. a. Stop data collection. Select OK. Add distilled water.025 M Fe(NO3)3 solution to the flask to make precisely 100 mL. To prepare a blank cuvette. Choose Linear as the Fit Equation.025 M Fe(NO3)3 solution to the flask to make precisely 100. Prepare the synthesized aspirin sample for testing. i.01 g. and select OK. Record the absorbance and concentration values in your data table. Add 0. then tap Mode. and transfer the rinse water to the volumetric flask. Record the mass of aspirin that you use to the nearest 0. e. Change the mode to Events with Entry.  In Logger Pro. Mix the solution thoroughly. After closing the lid. Click Abs vs. Add 150 mL of distilled water to the beaker. Choose Curve Fit from the Analyze menu. and then fill it 3/4 full. d. b. 22. Swirl the mixture to dissolve the solid. select Keep and enter the molar concentration. h. You are now ready to collect data for the five standard solutions. Select OK. After the preparation and testing of your aspirin sample in the following steps. Thoroughly rinse the beaker with several portions of distilled water. The graph should indicate a direct relationship between absorbance and concentration. The absorbance and concentration values have now been saved for the first solution. d. wait for the absorbance to stabilize and select Keep. Transfer 5 mL of the aspirin solution from the 250 mL volumetric flask to a clean and dry 100 mL volumetric flask. c. the displayed wavelength of maximum absorbance ( max) is automatically identified on your graph with a point protector. to fill the flask to the 250 mL mark. The wavelength of maximum absorbance ( max) will be selected. Add distilled water. You can do this either by examining your data points along the curve. b.4 g of aspirin and transfer it to the 250 mL beaker.0 mL. When the absorbance value displayed on the screen has stabilized. Enter the Name (Concentration) and Units (mol/L). Enter the molar concentration. concentration. Concentration as the Collection Mode. 21. Add 10 mL of ethanol to the beaker of aspirin sample. Using the solution in the second 100 mL volumetric flask. Wipe the outside. a. Select OK. place it in the device. a relationship known as Beer’s law. as needed. Measure out about 0. click the Configure Spectrometer button. g. Complete this step quickly and be ready to proceed directly to Step 23. rinse the cuvette twice with ~1 mL amounts. e. Mix the solution. Mix the solution thoroughly. you will be instructed to interpolate along this plot to determine the concentration of salicylic acid impurity in your aspirin sample. a. Select OK. and close the lid. Leave the Trial 1 cuvette in the Spectrophotometer and start data collection. Tap the Meter tab. Change the mode to Events with Entry (absorbance vs. Discard the cuvette contents as directed by your instructor. concentration) and select a wavelength for analysis:  In LabQuest App. Stop data collection to view a graph of absorbance vs. . Repeat the procedure for the remaining salicylic acid solutions that you prepared.c. Quantitatively transfer the solution from the beaker to a 250 mL volumetric flask. or by viewing the data table. c. The regression line should closely fit the five data points and pass through (or near) the origin of the graph. 6 Organics Chemistry with Vernier . f. a. b. To do this: a. Discard all solutions as directed. Monitor the absorbance value on the displayed Meter in Logger Pro (or tap the Meter tab in LabQuest). will be displayed to the right of the LabQuest graph. To determine the concentration of the salicylic acid impurity in the treated aspirin sample. Note: If the absorbance value does not fall within the range of the salicylic acid standard solutions in your data table. record it in your data table. c. in mol/L.08 g/mL) used (g) Mass of aspirin and filter paper (g) Mass of filter paper (g) Mass of aspirin synthesized (g) Part II Melting Temperature Data Melting temperature range (°C) Part III Salicylic Acid Standard Stock Solution Initial mass of salicylic acid (g) Moles of salicylic acid (mol) Initial molarity of salicylic acid (mol/L) Organic Chemistry with Vernier 7 . Measure and record the absorbance value of the treated aspirin sample. The corresponding salicylic acid concentration. Rinse and fill the cuvette 3/4 full with the sample. or on your Logger Pro graph. Choose Interpolate from the Analyze menu. interpolate along the regression line to convert the absorbance value of the unknown to concentration. 24. Record the concentration of salicylic acid in your data table. b. Click or tap any point along the regression curve (or use the ◄ or ► keys on LabQuest) to find the absorbance value that is closest to the absorbance reading you obtained in Step 23. Cap the cuvette and place it in the Spectrophotometer. This must be done within 10 minutes of completing Step 22.The Synthesis and Analysis of Aspirin 23. DATA TABLE Part I Synthesis of Aspirin Mass of salicylic acid used (g) Volume of acetic anhydride used (mL) Mass of acetic anhydride (1. If the absorbance value falls within the range of the salicylic acid standard solutions. you can repeat Step 22e using a more dilute or more concentrated solution. 25. Use your percent purity calculations to determine the percent yield of your synthesis of aspirin. Based on the results of the absorbance testing with the Spectrophotometer.Part III Beer’s Law Data for Salicylic Acid Standard Solutions Trial Concentration (mol/L) Absorbance 1 2 3 4 5 Test of the Purity of the Synthesized Aspirin Initial mass of aspirin sample (g) Absorbance of aspirin sample Concentration of salicylic acid (mol/L) Moles of salicylic acid in aspirin sample (mol) Mass of salicylic acid in aspirin sample (g) Mass of aspirin in sample (g) Percent aspirin in sample (%) DATA ANALYSIS 1. 8 Organics Chemistry with Vernier . 4. 2. Using a literature source or the internet. what is the percent purity of your sample of aspirin? Does this percent purity compare well with the results of the melting temperature test? Explain. What is the theoretical yield of aspirin in your synthesis? The mole ratio is 1:1 between salicylic acid and acetic anhydride in this reaction. find the accepted melting temperature value of pure acetylsalicylic acid. How does the melting temperature test of your aspirin compare to the accepted value? 3. Acetic anhydride: Strongly irritating and corrosive. HMIS Classification: Health hazard3. A low yield may not always be the result of sloppy work. Causes severe eye damage. www. Moderately toxic by ingestion and inhalation. It is critical for your students to complete the spectrophotometric analysis of their samples (Part III) in one lab period. HMIS Classification: Health hazard2. Flammability0.10 g of FeNO3•9H2O per 1 L. Flammability0. Addition of denaturant makes the product poisonous. HMIS Classification: Health hazard2. Open and dispense in fume hood. but poor lab technique will certainly result in a disappointing yield. if you wish to have them complete Parts II and III in the same lab period. Flammability2. Wear eye protection. Burns tissue. Each lab team will use about 2 g of salicylic acid. Causes serious eye damage. Phosphoric acid (o-phosphoric acid): Skin and eye irritant. May be harmful if swallowed. Physical hazard2. you will need to provide an air-flow supply (low flow) to fairly quickly air dry their aspirin sample. Causes mild skin irritation. Physical hazard1. Or. Flammable. Toxic by ingestion and inhalation. 5.sigmaaldrich.025 M Fe(NO3)3 solution can be prepared by using 10. Flammability0. Physical hazard0. HMIS Classification: Health hazard2. HMIS Classification: Health hazard3. they will need to dry the sample. Ethanol: Fire risk (flash point 14. Store in dedicated flammables cabinet. You may choose to have them wait until the next lab period. 1-800-325-3010. After students complete the Part 1 synthesis. 2. to ensure that the sample is dry. Moderately toxic by ingestion and inhalation. Flammability3. Moderate fire risk (flash point 49°C). Iron (III) nitrate: May intensity fire. 3.html Organic Chemistry with Vernier 9 . May cause respiratory irritation. oxidizer. Vapors are strongly irritating.. The hazard information reference is Sigma-Aldrich Co. Physical hazard0. The 0.0°C). Causes skin irritation. because of the instability of the prepped samples. HAZARD ALERTS Salicylic acid: Harmful if swallowed. 4. 6. You may choose to shorten Part III by providing your students with Beer’s law standards. Physical hazard3. Have access to eyewash. Reacts (sometimes delayed) violently with water.The Synthesis and Analysis of Aspirin INSTRUCTOR INFORMATION 1.com/safety-center/msds-search. Skin and eye irritant. The yield for this reaction will be lower than your students’ expectations. 277 Concentration of salicylic acid (mol/L) 1.50 × 10–4 Moles of salicylic acid in aspirin sample (mol) 1.10 Mass of aspirin in sample (g) 0.52 Mass of filter paper (g) 0.832 3 3.SAMPLE DATA Part I Synthesis of Aspirin Mass of salicylic acid used (g) 2.0 Mass of acetic anhydride (1.63 × 10–4 0.30 Percent aspirin in sample (%) 75 Organics Chemistry with Vernier .423 5 1.5 × 10–5 Mass of salicylic acid in aspirin sample (g) 0.47 × 10–4 0.56 Mass of aspirin synthesized (g) 1.16 × 10–4 0.40 Absorbance of aspirin sample 0.211 Test of the Purity of the Synthesized Aspirin 10 Initial mass of aspirin sample (g) 0.08 g/mL) used (g) 5.40 Mass of aspirin and filter paper (g) 2.79 × 10–4 1.96 Part II Melting Temperature Data Melting temperature range (°C) 132.616 4 2.6–133.005 2 4.00145 Initial molarity of salicylic acid (mol/L) 0.201 Moles of salicylic acid (mol) 0.9 Part III Salicylic Acid Standard Stock Solution Initial mass of salicylic acid (g) 0.32 × 10–4 0.00579 Part III Beer’s Law Data for Salicylic Acid Standard Solutions Trial Concentration (mol/L) Absorbance 1 5.01 Volume of acetic anhydride used (mL) 5. 50 × 10–4 mol/L.0146 mol mol of salicylic acid = mol of aspirin produced (theoretical) theoretical mass of aspirin produced = 0. the theoretical yield of aspirin is 2. The absorbance of 0. Thus. the mass of synthesized aspirin is 1.13 g/mol = 0.50 × 10–5 mol × (250/5) = 7. Corrected for purity. For the sample data.50 × 10–4 mol of salicylic acid in the initial aspirin sample. The mass of salicylic acid is: 7.47 g ÷ 2.16 g/mol = 2.9%.081. The absorbance of the aspirin sample is 0.13 g/mol = 0.63 g. The percent yield is: (1.01 g ÷ 138.50 × 10–5 mol.10 g of this sample is unreacted salicylic acid.75) = 1. Answers will vary.63 g) × 100 = 55. then the percent of aspirin in the sample is: (30 g/40 g) × 100 = 75%. The experimentally determined melting temperature of 132.0146 mol × 180.63 g 2. SAMPLE DATA Melting temperature determination for aspirin sample Organic Chemistry with Vernier 11 .96 × 0.081 equals a salicylic acid concentration of 1. The calculation is based on salicylic acid (the limiting reactant).The Synthesis and Analysis of Aspirin SAMPLE CALCULATIONS 1. mol of salicylic acid used = 2. the calculations are as follows. For the sample data.50 × 10–4 mol × 138. If 0.6°C compares well with the accepted melting temperature of pure acetylsalicylic acid. 4. This compares reasonably well with the melting temperature test. 135°C. The results of the spectrophotmetric test show that the percent purity of the synthesized aspirin is 75%. There was 1. For the sample data. Because the sample volume is 100 mL.50 × 10–5 mol of salicylic acid in a 5 mL sample. the molar amount of salicylic acid impurity in the aspirin sample is 1.96 g.40 g. 3. there is (1. is: (1.47 g.10 g The initial mass of the aspirin sample is 0. This 5 mL sample was taken from 250 mL of solution. Spectrum for salicylic acid with iron (III) nitrate Absorbance vs. concentration for salicylic acid with interpolation 12 Organics Chemistry with Vernier .