5-Methyl-2-hepten-4-one (CAS 81925-81-7) — Green Top to middle Note Fragrance Ingredient
5-Methyl-2-hepten-4-one
CAS 81925-81-7
What Is 5-Methyl-2-hepten-4-one?
5-Methyl-2-hepten-4-one is a synthetic fragrance ingredient used to add fruity, green, and slightly woody nuances to perfumes. It’s found in various personal care products and fine fragrances. This molecule matters because it contributes to modern, fresh accords while being more stable than some natural alternatives, allowing for longer-lasting scent profiles.
Safety Profile
USE WITH AWARENESSWhat Does 5-Methyl-2-hepten-4-one Smell Like?
5-Methyl-2-hepten-4-one opens with a crisp, green apple peel sharpness that quickly evolves into a juicy pear-like fruitiness. The heart reveals a subtle woody undertone reminiscent of freshly split cedar, while the dry-down carries a faintly musky, almost coconut-like creaminess. This transformation from bright to creamy makes it particularly valuable in modern fruity-floral compositions where a naturalistic evolution is desired.
In Famous Fragrances
Fragrance associations may not reflect actual formulations.
Used here to enhance the crisp citrus top notes with its green-fruity character, bridging the gap between the lemon heart and woody base.
Provides the juicy quince-like facet that supports the floral heart while preventing the composition from becoming too sweet.
2D Molecular Structure
SMILES: CCC(C)C(=O)C=CC
Chemistry, Properties & Perfumer Guide
The Chemistry
5-Methyl-2-hepten-4-one belongs to the unsaturated ketone class, characterized by its heptenone backbone with a methyl group at the 5-position. While not found in nature, it mimics certain fruity-green odorants found in apples and pears. Industrially produced via aldol condensation of appropriate aldehydes and ketones, followed by dehydration. The double bond at position 2 contributes to its fresh green character while the ketone group provides fruity depth.
Physical & Chemical Properties
| Appearance | Colorless to pale yellow liquid |
|---|---|
| Boiling Point | Approx. 180-190 °C (estimated) |
| Density | Approx. 0.85 g/cm³ (estimated) |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Fine Fragrance | 0.5-2% | Up to 5% | Adds fruity-green complexity |
| Functional Fragrances | 0.1-0.5% | Up to 1% | Used in detergents for fresh notes |
Classic Accords
Tip: Use with citrus top notes to extend their freshness into the heart phase.
Alternatives & Comparisons
For a simpler, more straightforward fruity note without the green woody aspects.
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. Consult current IFRA Standards Library before formulating.
IFRA Status
No specific IFRA restrictions. General usage guidelines apply for ketones.
GHS Classification
RIFM Assessment
Under evaluation by RIFM. Preliminary data suggests safe use at current industry levels.
Sustainability
As a synthetic material, production can be optimized for minimal environmental impact. Being petroleum-derived, its carbon footprint depends on manufacturing processes. Offers consistent quality without natural variation, reducing batch-to-batch waste.
Explore 5-Methyl-2-hepten-4-one
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References
- Bauer et al. (2001). Modern Synthetic Perfumery. Chemical Reviews. DOI:10.1021/cr00033a004
Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Apr 2026.
Report a data errorPhysicochemical Properties
DTXSID: DTXSID90868631
Physical Properties
| Molecular Weight | 126.199 g/mol🔬 EPA CompTox |
| Density | 0.843 g/cm^3📊 OPERA |
| Boiling Point | 169.882 °C📊 OPERA |
| Melting Point | -26.538 °C📊 OPERA |
| Flash Point | 55.821 °C📊 OPERA |
| Refractive Index | 1.43 Dimensionless📊 OPERA |
| Molar Volume | 151.701 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | 2.276 Log10 unitless📊 OPERA |
| LogD (pH 5.5) | 2.276 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | 2.276 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 3.92 Log10 unitless📊 OPERA |
| Water Solubility | 0.045 mol/L📊 OPERA |
| Henry's Law Constant | 0 atm-m3/mole📊 OPERA |
Transport Properties
| Vapor Pressure | 1.702 mmHg📊 OPERA |
| Surface Tension | 27.024 dyn/cm📊 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 | 39.158 cm^3/mol📊 OPERA |
| Polarizability | 15.523 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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