Question

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. OH HOOH 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 HO Ho stomach, but when esterified, as aspirin is, they are much better tolerated. Simple esters are rapidly cleaved in vivo (Latin, "in a living thing", in your blood etc.) 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. Salicin (in Willow) metabolism Salicylic Acid OH H3COCHE acetic anhydride 102 g/mol, 1.1 g/mL ОН Salicylic acid 138 g/mol Acetylsalicylic acid 180 g/mol cat. H3PO4 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 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. 6 Acetylsalicylic acid (Aspirin itself) may have its own activity aside from being a prodrug of salicylic acid. CUM 12 T ayoshirin SG

Pre-lab Questions:

Answer 1

Date Page Acetic anhydride is in excess. In above procedure 3 gm of salicylic acid f 6.0 ml of acetic anhydride is taken proportion of salicylic acid & acetic anhydride require is 1:1, therefore here excess acetic! anhydride is taken. i product (Aspirin) - Reactant (salicylic - acid) 138 g/mol 3.17 m - 180 g/mol 9 (coross multiplication) 3.17 x 180 1 = 4.13 m Product hormed when we reactant = 4.13 gm. take 3 17 gm - Phosphoric acid acts as a catalyst the rate of reaction. It protonate carboxyl group of salicylic acid f the esterification reaction. & fastens the favours Aspirin formed during reaction can be precipitase out when we add water le for precipitation purpose water is added.. lone another purpose is unreacted acetic anhydo de lalso converted to acetic acid by addition of water. Те си от Acetic anhydoide Walter Acetic acid Co

Date Page 6 Purpose of Fech test at the end : - The collected Aspirin will be tested for its purity using recl Salicylic acid contains a phenol group, but acetyl souscylic acid does not. Therefore if you add Fech to an aspirin sample of you see a purple colour It means that there is still some salicylic acid present of sample is impune Impure Sample & I lehen no purple IS completed & fecla colour we get - purple observed then aspirin.. colour reaction