5-Hexen-2-one (CAS 109-49-9) — Green Top Note Fragrance Ingredient
5-Hexen-2-one
CAS 109-49-9
What Is 5-Hexen-2-one?
5-Hexen-2-one is a synthetic fragrance ingredient with a green, fruity aroma. It’s primarily used in perfumery to add fresh, leafy nuances. You’ll encounter it in some modern citrus and floral fragrances where a crisp, natural greenness is desired.
Safety Profile
GENERALLY SAFEWhat Does 5-Hexen-2-one Smell Like?
5-Hexen-2-one delivers a sharp, green burst reminiscent of freshly crushed leaves with a subtle fruity undertone. The initial impression is intensely verdant, like the snap of a green apple stem, evolving into a cleaner, more ethereal green character. As it dries down, it maintains a crisp freshness without becoming harsh, making it useful for adding naturalistic green accents in floral compositions.
2D Molecular Structure
SMILES: CC(=O)CCC=C
Chemistry, Properties & Perfumer Guide
The Chemistry
5-Hexen-2-one is an unsaturated ketone with the molecular formula C6H10O. It’s synthesized through oxidation of corresponding alcohols or controlled pyrolysis of fatty acids. The molecule features a reactive double bond that contributes to its green character. As a synthetic material, it’s produced under controlled conditions to ensure purity and consistency.
Physical & Chemical Properties
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Fine Fragrance | 0.1-0.5% | Up to 1% | Green modifier |
| Functional Fragrance | 0.05-0.2% | Up to 0.5% | Freshness booster |
Classic Accords
Tip: Use sparingly to avoid overpowering green notes in delicate compositions.
Alternatives & Comparisons
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
Limited safety assessment available. Considered safe at current usage levels.
Sustainability
As a synthetic material, 5-Hexen-2-one has minimal environmental impact in production. Its efficient synthesis from petrochemical precursors makes it a sustainable choice compared to some natural green materials that require extensive agricultural resources.
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Ingredient Data Sheet
CAS 109-49-9Physical Properties
| Molecular Weight | 98.14 g/mol🔬 PubChem |
| LogP (Octanol-Water) | 1🔬 PubChem |
| Boiling Point | 128.5 °C🔬 EPA CompTox |
| Vapor Pressure | 10.5003 mmHg @ 25°C📊 OPERA |
| Flash Point | 23.9 °C🔬 EPA CompTox |
| Involatility Index | 1.1424💻 Calculated |
| log Kp (skin permeability) | -2.589💻 Calculated |
| SMILES | CC(=O)CCC=C🔬 PubChem |
Volatility & Performance
| Fragrance Note | Top💻 Calculated |
| Volatility Class | Fast💻 Calculated |
| Persistence Score | 0.5 / 5💻 Calculated |
Odor & Flavor
| Primary Descriptors | burntetherealfloralfruitypungent• leffingwell |
| Functional Groups | ketonealkene💻 RDKit |
Physical data: PubChem (NIH/NLM), U.S. EPA CompTox Dashboard, EPA OPERA models, RDKit. Odor & flavor: Arctander (Perfume & Flavor Chemicals), Fenaroli's Handbook of Flavor Ingredients, Leffingwell. Thresholds: van Gemert (Compilations of Odour Threshold Values). Regulatory: IFRA Standards 51st, FEMA GRAS. Trade names: Surburg (Common Fragrance & Flavor Materials). All data compiled and cross-referenced for perfumertools.com.
Physicochemical Properties
DTXSID: DTXSID0059372
Physical Properties
| Molecular Weight | 98.145 g/mol🔬 EPA CompTox |
| Density | 0.84 g/cm^3🔬 EPA CTX |
| Boiling Point | 129 °C🔬 EPA CTX |
| Melting Point | -57.895 °C📊 OPERA |
| Flash Point | 23.683 °C🔬 EPA CTX |
| Refractive Index | 1.409 Dimensionless📊 OPERA |
| Molar Volume | 119.789 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | 1.02 Log10 unitless🔬 EPA CTX |
| LogD (pH 5.5) | 1.011 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | 1.011 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 3.65 Log10 unitless📊 OPERA |
| Water Solubility | 0.211 mol/L📊 OPERA |
| Henry's Law Constant | 0 atm-m3/mole📊 OPERA |
Transport Properties
| Vapor Pressure | 10.5 mmHg🔬 EPA CTX |
| Viscosity | 0.516 cP📊 OPERA |
| Surface Tension | 25.073 dyn/cm📊 OPERA |
| Thermal Conductivity | 145.345 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 | 29.601 cm^3/mol📊 OPERA |
| Polarizability | 11.735 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.
