Acetylsalicylic acid
[CAS 50-78-2]

Identification

• Classification: API >> Antipyretic analgesics >> Antipyretic and analgesic
• Name: Acetylsalicylic acid
• Synonyms: 2-Acetoxybenzoic acid; Aspirin
• Molecular Formula: C₉H₈O₄
• Molecular Weight: 180.16
• CAS Registry Number: 50-78-2
• EC Number: 200-064-1
• SMILES: CC(=O)OC1=CC=CC=C1C(=O)O

Properties

• Density: 1.3±0.1 g/cm³ Calc.^*, 1.35 g/mL (Expl.)
• Melting point: 134 - 136 °C (Expl.)
• Boiling point: 321.4±25.0 °C 760 mmHg (Calc.)^*, 140 °C (Decomposes) (Expl.)
• Flash point: 131.2±16.7 °C (Calc.)^*, 250 °C (Expl.)
• Solubility: DMSO: 36 mg/mL, Water: <1 mg/mL (Expl.)
• Index of refraction: 1.551 (Calc.)^*

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software.

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H302-H315-H319-H335
• Safety Statements: P261-P264-P264+P265-P270-P271-P280-P301+P317-P302+P352-P304+P340-P305+P351+P338-P319-P321-P330-P332+P317-P337+P317-P362+P364-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Acute toxicity	Acute Tox.	4	H302
Eye irritation	Eye Irrit.	2	H319
Skin irritation	Skin Irrit.	2	H315
Specific target organ toxicity - single exposure	STOT SE	3	H335
Acute toxicity	Acute Tox.	3	H301
Reproductive toxicity	Repr.	1B	H360
Reproductive toxicity	Repr.	2	H361
Respiratory sensitization	Resp. Sens.	1	H334
Reproductive toxicity	Repr.	1A	H360
Specific target organ toxicity - single exposure	STOT SE	3	H336
Skin sensitization	Skin Sens.	1	H317
Specific target organ toxicity - single exposure	STOT SE	2	H371
Specific target organ toxicity - repeated exposure	STOT RE	2	H373

• Transport Information: UN 1851

chemBlink Chemical Story

Acetylsalicylic acid, universally known as aspirin, is one of the most influential molecules in the history of medicine. More than simply an effective pain reliever, it transformed pharmaceutical manufacturing, revealed fundamental mechanisms of inflammation, and reshaped the prevention of cardiovascular disease. Few chemical compounds have exerted such a profound and lasting influence on both science and public health.

The story of aspirin began long before the compound itself was synthesized. For centuries, extracts of willow bark and other salicylate-containing plants were used in traditional medicine to relieve pain and fever. During the nineteenth century, chemists isolated salicin from willow and subsequently converted it into salicylic acid, providing one of the earliest examples of transforming a traditional herbal remedy into a defined chemical substance. Although effective, salicylic acid frequently caused gastrointestinal irritation, limiting its clinical usefulness.

In 1897, Felix Hoffmann, working at Bayer, prepared a highly purified form of acetylsalicylic acid by acetylating salicylic acid. The modification greatly improved tolerability while preserving therapeutic activity. Bayer introduced aspirin commercially in 1899, and it rapidly became one of the world's first internationally recognized pharmaceutical brands. Its success demonstrated that medicines could be manufactured reproducibly, distributed globally, and marketed under consistent quality standards, helping establish the modern pharmaceutical industry.

For decades, physicians relied on aspirin to relieve pain, reduce fever, and treat inflammatory diseases without fully understanding its molecular mechanism. A major breakthrough came in 1971 when John R. Vane demonstrated that aspirin inhibits the biosynthesis of prostaglandins by blocking cyclooxygenase activity. This discovery transformed the understanding of inflammation and laid the foundation for modern research on nonsteroidal anti-inflammatory drugs. Vane shared the 1982 Nobel Prize in Physiology or Medicine for this work, highlighting aspirin's contribution not only to therapy but also to fundamental biomedical science.

Aspirin's scientific significance expanded further with the recognition that low doses irreversibly inhibit platelet aggregation. This finding established aspirin as an effective agent for reducing the risk of recurrent myocardial infarction and ischemic stroke in appropriate patients. The discovery changed preventive cardiovascular medicine and remains one of the most important examples of drug repurposing, in which a well-known medicine acquires major new clinical applications decades after its introduction.

Today, aspirin continues to be used worldwide despite the availability of numerous newer analgesics and anti-inflammatory drugs. Its enduring importance reflects a unique combination of historical influence, scientific discovery, and clinical utility. From the transition of herbal medicine to standardized pharmaceuticals, through the elucidation of inflammatory signaling, to the prevention of cardiovascular disease, acetylsalicylic acid has repeatedly transformed medical practice. It remains one of the defining pharmaceutical milestones of modern chemistry and medicine.

**References**

1. Vane, J. R. (1971). "Inhibition of prostaglandin synthesis as a mechanism of action for aspirin-like drugs." *Nature New Biology*, 231, 232-235.

2. Sneader, W. (2000). "The discovery of aspirin: a reappraisal." *BMJ*, 321, 1591-1594.

3. Patrono, C. et al. (2017). "Low-dose aspirin for the prevention of atherothrombosis." *New England Journal of Medicine*, 377, 2503-2515.