Exp. 11 (2 meetings): Synthesis of Aspirin and Melting Point Determination
1. What is the melting point range of your aspirin sample?
2. What were the results of your FeCl3 tests when you compared the aspirin you made to the commercial aspirin?
3. Do the results of your melting point determination agree with the results from your FeCl3 test? Explain.
POST-LAB QUESTIONS:
1. Give two physical properties you observed in your crude (unpurified) aspirin sample.
2. If the theoretical yield of a reaction was calculated to be 3.11g and the actual yield was 2.65g, what was the percent yield for the reaction? Show formula and all work.
3. If a melting point range is greater than 3o C, such as 119.5o C to 125.8o C, what can you say about the sample?
Coution! The preporation of aspirin involves the use of two hozardous materials- concentrated sulfuric ocid anhydride, These chemicols should be in Hood 7-do not remove from Hood 7 SYNTHESIS OF ASPIRIN (acetylsalicylic acid): 1. Set up a hot water bath (boiling) using a 400mL beaker filled with tap water on a hot plate water you will 2. Using a metal bowl from the drawers under the hoods, start an ice water bath so the i 3. Using a top loading balance, mass out approximately 2.50 g of salicylic acid. If you use a di 4 s, start an ice water bath so the ice-cold need later will be cool enough, You will also use this as an ice bath sposable weight beat mass (vou will need it be sure to tare/re-zero the weigh boat before adding the salicylic acid Record the precise mass ( to calculate the % yield) in the data table Place the salicylic acid in a clean and dry 125 ml Erlenmeyer flask me concentrated H2saa and acetic anhydridew remain in Hood 7. Using cylinder, carefuly altern Place the tethe%acid inin thedatatable125 mLErien ever tas 4 a clean and dry 10 mL graduated 5. to the flask 6 Add 7:2 dreps of concentrated HsQ4 (sulfuric acid) to the (sulfuric acid) to the flask mixture thoroughly and place Erienmeyer into the hot water bath if the water is boiling. Take acid remains dissolved (no solid is present) the hot water bath and allow to cool for 3.5 minutes (you may see white solid begin to Gently swirl the care to ensure that the reaction flask does 7. r not tip to allow water in it. If this happens, you will need to start Swirl frequently or stir with a glass rod to ensure the solid salicylic and continue heating in boiling bath for 10 minutes. Remove the flask from the hot water bath and allow to cool for 3-5 minutes (you may see white crystallize). 8. 9. Calculate the theoretical yield of the product (1 mole salicylic acid 135g. 1 mole of acetyl salicylic acid 180g). Show 38g SA 10. Tilt the mouth of the ask away from Vou and add approximately S ml of ICE CoLD water to the flask After you've decomposed the excess acetic anbydride, add 40 ml of ICE COLD water to the flask, swirl, and let the flask sit at to room temperature, undisturbed, for approximately 3-5 minutes (this allows the aspirin crystals to grow). Aspirin crystals should form as the flask cools Observations- What do you see in the flask: watey 11. Gently lower the flask containing your aspirin crystals into the CE BATH to cool the liquid so more aspirin crystals can crystallize out of the solution (do not allow any additional water inside the flask). Let the crystals continue to form in the ice water bath for approximately 10 more minutes ust ice cout vatemx roughly, and place the peskeratnettndturbed ntl erystal 12. While waiting for all of the aspirin to crystallize out of the solution, record the mass of a piece of filter paper (size: 70 mm). You will use this piece of flter paper with the Buchner funnel /vacuum filtration to isolate your aspirin crystals Collect Buchner funnel, black or grey adapter to achieve a good seal, vacuum hose, filter flask, ring stand, and your massed filter paper and assemble next to a sink with an aspirator adapter V02 3 V 02 3
