Question

1) Which reactant, salicylic acid or acetic anhydride, is in excess? Show your work.

2) If you were to use 3.17 g of starting material, how much product would you expect? Again, show your work.

3) Why is phosphoric acid added to the reaction?

4) A small amount of water is added at the end of the reaction to react with the excess acetic anhydride. Show a balanced equation for that reaction.

5) Explain the purpose of the FeCl3 test at the end and what the expectation is.

Lab Day 10: Aspirin, Synthesis of an Important Medicine Prelab Read and understand the entire day's background and lab procedure. Study McMurry, Sections 17.4-17.6. Your Lab Notebook As you prepare for this lab, enter notes from your reading of the experimental procedure, including any pertinent information from any prelab reading and/or videos and any questions you need to ask during the prelab presentation, in your lab notebook Importance A one-step preparation of aspirin from its precursor, salicylic acid, via an ester formation illustrates one of synthetic organic chemistry's most important uses, making the drugs that treat all types of illnesses. Background Aspirin is a prodrug of salicylic acid, the actual active drug. A compound related to salicylic acid, salicin, was first isolated from willow bark in the mid 1700's, but willow-bark extract was used by the ancient Greeks as a treatment for pain and fever. Salicylic acid (and many related phenols) are very hard on your stomach, but when esterified, as shown for the preparation of aspirin below, they are much better tolerated. Simple esters are rapidly cleaved in vivo to generate, in this case, the free phenol. Even though aspirin has been around longer than most other drugs, it remains an important drug, especially since daily low doses are now known to prevent the recurrence of heart attacks он Salicin (in Willow) metabolism Salicylic Acid HO он он acetic anhydride 102 g/mol, 1.1 g/mL O Acetylsalicylic acid он Salicylic acid 138 g/mol 180 g/mol cat HaPO Esterification reactions are formally a condensation reaction of a carboxylic acid and an alcohol or phenol. In the example here, acetic anhydride is used as an activated form of acetic acid to make the reaction easier. Acetic anhydride is used as the solvent as well as a reactant, and a small amount of concentrated phosphoric (85% is standard, the 15% water being easily removed by reaction with some of the acetic anhydride) is used to promote the reaction. Phosphoric acid is not formally a "strong acid", but it almost is, and is safer than the sometimes-used sulfuric acid Chemicals and Equipment Salicylic acid, 125 mL Erlenmeyer flask, acetic anhydride,concentrated phosphoric acid, vented stopper, hot-water bath (400 mL beaker of water, hot plate), heat-resistant gloves, ice bath, filter paper, Büchner funnel, vacuum flask, watch glass, drying oven, acetylsalicylic acid (reference compound), FeCl solution, melting point tubes, Mel-temp Safety Issues Concentrated phosphoric acid and acetic anhydride are reactive; any spillage should be reported immediately, and contaminated skin should be washed with a large about of water Waste Disposal The aqueous waste can be diluted with water and flushed down the sink with the water running. The product and filter paper should be put in the dedicated beaker labeled for aspirin waste Acetylsalicylic acid (Aspirin itself) may have its own activity aside from being a prodrug of salicylic acid 51

Answer 1

enese disethom SA Hslu3-1 " J ① fussphanic oudu.unda, a Cataly, I'm the rH 너 ナ。 Grty 1 3 H9 3 salicylic aeid yello VLo pu