3-Hexenal (CAS 4440-65-7) — Green Top Note Fragrance Ingredient
3-Hexenal
CAS 4440-65-7
What Is 3-Hexenal?
3-Hexenal is a synthetic fragrance ingredient that creates fresh, green aromas reminiscent of crushed leaves or cut grass. You’ll encounter it in perfumes, candles, and household products where a natural green character is desired. This molecule matters because it captures the fleeting scent of nature – the exact smell of a freshly torn leaf – with remarkable precision, allowing perfumers to recreate botanical freshness without harvesting plants.
Safety Profile
GENERALLY SAFEWhat Does 3-Hexenal Smell Like?
3-Hexenal bursts forth with an intensely green, almost violent verdancy – the olfactory equivalent of snapping a celery stalk in half, amplified tenfold. Its piercing top note evokes dew-laden grass at dawn, with a slightly waxy undertone reminiscent of greenhouse plastic. As it evolves, the harshness mellows into a cleaner, cucumber-like wateriness, though never losing its vegetal core. The dry-down is surprisingly persistent for such a volatile molecule, leaving behind a faint memory of herbal tea steeping in a sunlit kitchen.
2D Molecular Structure
SMILES: CCC=CCC=O
Chemistry, Properties & Perfumer Guide
The Chemistry
3-Hexenal belongs to the α,β-unsaturated aldehyde class, characterized by a double bond adjacent to the carbonyl group. This structural feature makes it highly reactive and responsible for its intense green odor. Industrially produced via oxidation of corresponding alcohols or controlled aldol condensation reactions. The (E)-isomer dominates commercial production due to greater stability, though both isomers occur in nature as leaf alcohol metabolites.
Physical & Chemical Properties
| Boiling Point | ~150 °C (estimated) |
|---|---|
| Density | ~0.85 g/cm³ (estimated) |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Fine Fragrance | 0.1-0.5% | Up to 1% | Powerful green modifier |
| Functional Fragrance | 0.01-0.1% | Up to 0.3% | Freshness booster |
Classic Accords
Tip: Stabilize in ethanol before blending to prevent polymerization.
Alternatives & Comparisons
Less intense green character without aldehyde sharpness, preferred for softer applications.
Synthetic green with better stability and less harshness, though less naturalistic.
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. Consult current IFRA Standards Library before formulating.
IFRA Status
Not restricted under current IFRA standards.
RIFM Assessment
Recognized as safe at current usage levels based on structural analogs.
Sustainability
Synthetic production avoids plant harvesting but requires petrochemical feedstocks. New bio-based routes under development using fermentation of hexenols. Low environmental persistence due to rapid atmospheric degradation.
Explore 3-Hexenal
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References
- Burdock, G.A. (2010). Fenaroli’s Handbook of Flavor Ingredients. CRC Press.
- Arctander, S. (1969). Perfume and Flavor Chemicals. Allured Publishing.
Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Apr 2026.
Report a data errorPhysicochemical Properties
DTXSID: DTXSID2063470
Physical Properties
| Molecular Weight | 98.145 g/mol🔬 EPA CompTox |
| Density | 0.975 g/cm^3🔬 EPA CTX |
| Boiling Point | 121 °C🔬 EPA CTX |
| Melting Point | 126 °C🔬 EPA CTX |
| Flash Point | 32.572 °C📊 OPERA |
| Refractive Index | 1.422 Dimensionless📊 OPERA |
| Molar Volume | 118.509 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | 1.428 Log10 unitless📊 OPERA |
| LogD (pH 5.5) | 1.428 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | 1.428 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 3.65 Log10 unitless📊 OPERA |
| Water Solubility | 0.073 mol/L📊 OPERA |
| Henry's Law Constant | 0 atm-m3/mole📊 OPERA |
Transport Properties
| Vapor Pressure | 12.473 mmHg📊 OPERA |
| Viscosity | 0.595 cP📊 OPERA |
| Surface Tension | 24.786 dyn/cm📊 OPERA |
| Thermal Conductivity | 145.408 mW/(m*K)📊 OPERA |
Molecular Descriptors
| Topological Polar Surface Area | 17.07 Ų💻 Computed |
| H-Bond Donors | 0 count💻 Computed |
| H-Bond Acceptors | 1 count💻 Computed |
| Rotatable Bonds | 3 count💻 Computed |
| Aromatic Rings | 0 count💻 Computed |
| Molar Refractivity | 30.091 cm^3/mol📊 OPERA |
| Polarizability | 11.929 Å^3📊 OPERA |
Data Sources:
🔬 EPA Experimental data from U.S. EPA CompTox Chemicals Dashboard & CTX APIs. 📊 OPERA Predicted using EPA's OPERA QSAR models. 💻 Computed Calculated from SMILES using RDKit.
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