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 matters because coumarin's sweet hay-like odor helped shape synthetic perfumery, while derivatives of the same benzopyrone scaffold later produced very different biology such as 4-hydroxycoumarin anticoagulants. This connection between molecular structure and observable behavior is more informative than a simple list of uses. CAS 91-64-5 identifies the substance in this chemBlink record, while its practical significance comes from the way its functional groups, composition, or material structure control reactivity and physical properties.

The broader lesson is that chemical identity alone does not determine performance. Conditions such as pH, temperature, formulation, concentration, molecular distribution, or biological environment can decide whether the same underlying chemistry is useful, inactive, or hazardous. For chemists, Coumarin is therefore a useful case study in connecting molecular-scale behavior with a real laboratory, industrial, biological, or materials-science outcome.

References: IARC/NCBI Bookshelf: Coumarin, CAS 91-64-5; RIFM safety assessment 2019

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