Aspirin
Properties
| State | Solid (white crystalline powder or tablets) |
| Color | White |
| Solubility | Slightly soluble in water (3 g/L at 20°C); soluble in ethanol |
| Melting Point | 135°C (decomposes above 140°C) |
| Boiling Point | Decomposes before boiling |
About Aspirin
Aspirin is the acetylated derivative of salicylic acid, and the small structural change — replacing the phenolic hydroxyl with an acetyl ester — is what made it a viable drug. Salicylic acid itself was used medicinally throughout the 19th century but caused enough gastric irritation that long-term use was difficult; the acetylation, achieved by Felix Hoffmann at Bayer in 1897, dramatically reduced the gastric side effects while preserving the analgesic and antipyretic activity. The mechanism that underlies aspirin's pharmacology was worked out only in 1971 by John Vane, who showed that aspirin irreversibly acetylates a serine residue (Ser530 in COX-1) in the active site of cyclooxygenase, blocking the enzyme's ability to convert arachidonic acid into prostaglandin precursors. The irreversibility is what makes aspirin's antiplatelet effect last for the lifespan of the platelet (7–10 days): platelets can't synthesize new COX, so a single low-dose aspirin shuts down their thromboxane production until they're replaced. The acetyl-on-serine chemistry is one of the cleanest mechanistic stories in medicinal chemistry, and it makes aspirin the textbook example of a covalent inhibitor. The molecule is also the canonical undergraduate organic chemistry synthesis: salicylic acid plus acetic anhydride with a few drops of phosphoric acid catalyst gives crystalline aspirin in about an hour, and students can take their product all the way through recrystallization, melting-point determination, and FTIR confirmation in a single afternoon.
Where you'll encounter it
If you take a low-dose (81 mg) aspirin daily for cardiovascular prevention, you're exploiting the irreversibility of COX-1 acetylation — the daily dose is just enough to keep newly produced platelets shut down without affecting other COX-dependent processes much. In the undergraduate chemistry teaching lab, the aspirin synthesis is often the second or third experiment of the semester, partly because it produces a crystalline product students can hold in their hands and partly because the reaction sequence (esterification, acid catalysis, recrystallization, characterization) packages most of the introductory organic-chemistry techniques into one experiment. In the global pharmaceutical supply chain, aspirin is one of the rare drugs where the manufacturing process is so well-developed that bulk pricing has fallen below the cost of the packaging it ships in.
Common Uses
- Analgesic and antipyretic at standard 325–650 mg adult doses
- Antiplatelet agent at low (81 mg) cardiovascular-prevention doses
- Anti-inflammatory at higher (3–6 g/day) dosing for rheumatic disease
- Standard undergraduate organic-chemistry synthesis target
- Reference compound for irreversible-inhibitor enzyme mechanism teaching
Safety Information
GI bleeding is the dominant chronic adverse effect — aspirin's COX-1 inhibition reduces the protective gastric prostaglandins, and long-term use produces a measurable rate of upper-GI bleeding even at low cardioprotective doses. The drug is contraindicated in children with viral illness because of the association with Reye's syndrome (a rare but severe encephalopathic-hepatic syndrome), and patients with documented salicylate hypersensitivity should avoid it. Acute overdose produces salicylate toxicity (tinnitus, hyperventilation, metabolic acidosis) at plasma levels above ~30 mg/dL.
This safety summary is for educational reference only and may not be complete. It is not a substitute for Safety Data Sheets (SDS), medical advice, or professional chemical safety guidance. Always consult appropriate SDS and qualified professionals before handling chemicals.