Coumarin
[CAS 91-64-5]

Identification

• Classification: Organic raw materials >> Hydrocarbon compounds and their derivatives >> Cyclic hydrocarbon
• Name: Coumarin
• Synonyms: 2H-1-Benzopyran-2-one
• Molecular Formula: C₉H₆O₂
• Molecular Weight: 146.14
• CAS Registry Number: 91-64-5
• EC Number: 202-086-7
• SMILES: C1=CC=C2C(=C1)C=CC(=O)O2

Properties

• Density: 1.2±0.1 g/cm³ Calc.^*, 0.935 g/mL (Expl.)
• Melting point: 68 - 73 °C (Expl.)
• Boiling point: 298.0 °C 760 mmHg (Calc.)^*, 298 °C (Expl.)
• Flash point: 118.3±16.1 °C (Calc.)^*, 162 °C (Expl.)
• Solubility: water 1.7 g/L (20 °C) (Expl.)
• Index of refraction: 1.595 (Calc.)^*

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

Safety Data

• Hazard Symbols: GHS06;GHS07 Danger
• Risk Statements: H301-H302-H317
• Safety Statements: P261-P264-P270-P272-P280-P301+P316-P301+P317-P302+P352-P321-P330-P333+P317-P362+P364-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Skin sensitization	Skin Sens.	1	H317
Acute toxicity	Acute Tox.	4	H302
Acute toxicity	Acute Tox.	3	H301
Specific target organ toxicity - repeated exposure	STOT RE	2	H373
Acute toxicity	Acute Tox.	3	H311
Chronic hazardous to the aquatic environment	Aquatic Chronic	3	H412
Skin sensitization	Skin Sens.	1B	H317
Chronic hazardous to the aquatic environment	Aquatic Chronic	2	H411
Acute toxicity	Acute Tox.	3	H331
Carcinogenicity	Carc.	2	H351
Acute toxicity	Acute Tox.	1	H300
Skin irritation	Skin Irrit.	2	H315
Serious eye damage	Eye Dam.	1	H318
Acute toxicity	Acute Tox.	4	H312
Eye irritation	Eye Irrit.	2	H319

chemBlink Chemical Story

Coumarin links a fragrant natural product, a foundational organic reaction, and the birth of modern synthetic perfumery. The compound occurs naturally in tonka beans and other plants and has a sweet, warm odor often compared with freshly cut hay. It was isolated in the early nineteenth century, but its most consequential chemical chapter began in 1868, when William Henry Perkin reported a synthesis from salicylaldehyde and acetic anhydride.

That transformation became known as the Perkin reaction. An aromatic aldehyde reacts with an acid anhydride in the presence of a carboxylate base to form an alpha,beta-unsaturated carboxylic-acid derivative; with salicylaldehyde, intramolecular lactonization produces the fused benzopyrone ring of coumarin. The reaction became a classic method for constructing cinnamic-acid derivatives and demonstrated how a recognizable natural odorant could be made from simpler chemical feedstocks.

Synthetic coumarin soon changed perfumery. Natural fragrance materials had been limited by harvest, geography, price, and variable composition. Industrially produced coumarin provided perfumers with a consistent hay-like note and was used prominently in Houbigant's Fougere Royale in 1882, a fragrance historically associated with the creation of the fougere family. Coumarin therefore helped shift perfumery from recombining natural extracts toward designing scents with synthetic molecules that need not imitate one specific flower.

The coumarin ring also became a major medicinal-chemistry scaffold, but an important distinction is often lost in popular discussion: coumarin itself is not the same substance as the anticoagulant warfarin. Warfarin and related anticoagulants are substituted 4-hydroxycoumarin derivatives whose biological activity depends on additional structural features. Sharing a heterocyclic core does not make all members of a chemical family pharmacologically equivalent.

Coumarin matters because it sits at a turning point in both chemistry and culture. Perkin's synthesis helped establish a named carbon-carbon bond-forming reaction; industrial coumarin helped make synthetic fragrance an independent creative medium; and the benzopyrone scaffold later spread through medicinal and natural-product chemistry. A molecule first valued because it smelled like hay became evidence that synthesis could reproduce nature - and then go beyond it.

References:
Perkin WH. Journal of the Chemical Society. 1868. Classical synthesis of coumarin by the Perkin reaction.
Synthesis of odorants in flow and their applications in perfumery. Beilstein Journal of Organic Chemistry. 2022;18:832-859. DOI: 10.3762/bjoc.18.76.
David O. European Journal of Organic Chemistry. 2023. DOI: 10.1002/ejoc.202300900.

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