1. IB Chemistry Option D Aspirin

2. Aspirin: Mild Analgesic Mild Analgesic – act at the source of pain by inhibiting production of chemical messengers that causes the sensation of pain, swelling, and fever. – Aspirin (and ibuprofen) prevents the production of prostaglandins by inhibiting an enzyme known as cyclooxygenase (COX), a key enzyme in the synthesis of prostaglandins. Prostaglandins – cause physiological effects in the body: – Induction of pain – Inflammation – fever

3. What is Aspirin? 5 th Century B.C.E. people chewed the bark of a Willow Tree for pain relief. – Contains a sugar derivative of salicylic acid (2- hydroxybenzoic acid). Converts into salicylic acid in the body. – Good analgesic, but with unfavorable side –effects: » Severe irritation of the stomach lining resulting in: Vomiting Gastric bleeding. Acetylsalicylic acid (Aspirin) – an ester of salicylic acid: – Less irritating to the stomach lining. Used all over the world as analgesic and anti- inflammatory agent.

4. Some Other Benefits of Aspirin Taken in low doses can help prevent recurrent heart attacks and strokes. – Protection through its anti-blood-clotting effect (acts as an anticoagulant). Low doses my help prevent certain cancers. Aspirin is prophylactic – something taken to help prevent a disease from happening in the first place.

5. Synthesis of Aspirin Addition-elimination – type of reaction where CH 3 CO group is added to aspirin and ethanoic acid is eliminated.

6. Calculating Yield of Aspirin Be sure to look at pages 11 and 12 for an example of solving the yield of aspirin. (Solving for percentage yield.)

7. Purification of Aspiirin Recrystallization – where a solid is soluble in a solvent at a higher level but less soluble at a lower temperature. – Impurities will remain in solution at the lower temperatures, while the desired solid comes out of solution.

8. Recrystallization Procedure Product dissolved in minimum amount of hot solvent (near-saturated solution). Solution filtered while still hot to remove insoluble impurities. (Vacuum filtration used) Solution allowed to cool and product comes out of solution in form of solid crystals. Remaining solid product separated by vacuum filtration. Impurities remain in solution at lower temperatures.

9. Characterization of Aspirin Full characterization of Aspirin involves determining its: – Purity – Molecular formula – Physical properties – Structure – Etc.

10. Determination of the Purity of Aspirin Chromatography Measuring its Melting Point (MP) – Pure substance will melt at well defined temperatures. Presence of impurities lowers MP – Causes solid to melt over a range of temperatures. – Melting point of Aspirin: 138-140 o C If sample is tested with MP range of 125-132 o C it can be concluded that sample contains impurities.

11. Infrared Spectrum of Aspirin Used to help determine which bonds/functional groups are present in a molecule. Also used for comparison with spectra databases to determine if desired compound has been synthesized. – See Page 14 for graph data and explanation.