Question

EXPERIMENT 19 PREPARATION OF ASPIRIN In addition to the Fischer esterification method presented in Experiment 18, a second method for preparation of esters involves the reaction of anhydrides with the hydroxyl This method is ospecialy usoful for tho preparation of acetate esters, since acetic anhydride is an inexpensive and reactive reagent. In this experiment the hydroxyl group of salicylic acid is acetic anhydride to make acetylsalicylic acid, or aspirin. The short reaction time allows this be carried out during the reflux poriod of a Fischer esterification (Experiment 18), it desired. group of alcohols or phenols. estenitied with CH HaPO4 Salicylic acid Acetic anhydride Enough aspirin to make about 50 billion standard tablets is produced in the U.S. each year Aspirin is primarily an analgesic (pain-relieving) and antipyretic (fever-reducing) agent, but nevw medical findings about aspirin preventing heart attacks and colon cancer, for example. Excesses can cause internal bieeding. appear every year, and reports in the 1990s claim it to be beneficial in Physical Constants mol. wt. (g/mole) mp(c) density (g/mL) 158-161 138.12 Acetic anhydride 102.09 Acetylsalicylic acid 180.16 Sallicylic acid bp138-140 1.082 135 Experimental Procedure (small scale) In a 50-mL Erlenmeyer flask place 1.0 g of salicylic acid and carefully add 2 mL of acetic anhydride and 3 drops of concentrated phosphoric acid. Swirl the flask to mix the reagents and heat it in a hot-water bath (80-100 °C) for 15 minutes. Remove the flask from the hot-water bath and, while it is still warm, add about 10 drops of water one drop at a time, swirling the flask after each addition. The water reacts vigorously with the excess acetic E19-1
find the theoretical yield of the acetysalicylic acid .

Answer 1

Moles of salicylic acid = 1.0//138 = > 0.00725 moles Then moles of acetyl salicylic acid formed = 0.00725 Theoretical yield of acetyl salicylic acid = 0.00725 times 180 = 1.305 g