6-Methyl-3,5-heptadien-2-one (CAS 1604-28-0) — Green Top to middle Note Fragrance Ingredient
6-Methyl-3,5-heptadien-2-one
CAS 1604-28-0
What Is 6-Methyl-3,5-heptadien-2-one?
6-Methyl-3,5-heptadien-2-one is a synthetic fragrance ingredient used to add green, herbal nuances to perfumes and scented products. You’ll encounter it in fresh fougères, modern florals, and citrus colognes. This molecule matters because it provides a crisp, slightly woody-green character that helps bridge citrus top notes with floral heart notes in complex fragrances.
Safety Profile
GENERALLY SAFEWhat Does 6-Methyl-3,5-heptadien-2-one Smell Like?
6-Methyl-3,5-heptadien-2-one opens with a sharp, green burst reminiscent of freshly crushed tomato leaves and unripe walnuts. The initial pungency quickly settles into a dry, woody-herbal character with subtle citrus undertones. As it evolves, it reveals a faintly floral aspect akin to chamomile tea leaves. The dry-down is clean and slightly peppery, leaving a transparent woody trail that blends seamlessly with other materials without overpowering them.
In Famous Fragrances
Fragrance associations may not reflect actual formulations.
Used here to enhance the fragrance’s signature violet leaf accord, adding crispness to the green top notes while supporting the transition to the floral heart.
Provides a modern green counterpoint to the classic citrus-herbal structure, helping bridge the lemon top to the woody base notes.
2D Molecular Structure
SMILES: CC(C)=CC=CC(C)=O
Chemistry, Properties & Perfumer Guide
The Chemistry
6-Methyl-3,5-heptadien-2-one belongs to the class of unsaturated ketones with a conjugated diene system. This structure contributes to its reactivity and distinctive odor profile. Synthesized through aldol condensation reactions, it’s valued for its ability to introduce green, herbal nuances without the heaviness of traditional pyrazines. The molecule’s planar structure allows it to interact effectively with olfactory receptors responsible for detecting green and woody notes.
Physical & Chemical Properties
| Appearance | Colorless to pale yellow liquid |
|---|---|
| Boiling Point | Approx. 180-190 °C (estimated) |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Fine Fragrance | 0.5-2% | Up to 5% | Used as green modifier |
| Functional Fragrances | 0.1-0.5% | Up to 1% | For fresh herbal effects |
Classic Accords
Tip: Use sparingly in citrus compositions to add dimensionality without overpowering delicate top notes.
Alternatives & Comparisons
Offers similar green effects with greater diffusion and less sharpness, better for mainstream applications.
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. Consult current IFRA Standards Library before formulating.
IFRA Status
No IFRA restrictions currently apply to this material.
RIFM Assessment
Not currently evaluated by RIFM due to low production volumes.
Sustainability
As a synthetic material, 6-Methyl-3,5-heptadien-2-one has minimal environmental impact in production. Its efficient use at low concentrations makes it a sustainable choice for green notes compared to some natural alternatives that require agricultural resources.
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References
- Brenna et al. (2002). Structure-Odor Relationships in Unsaturated Ketones. Journal of Agricultural and Food Chemistry. ACS Publication
Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Apr 2026.
Report a data errorPhysicochemical Properties
DTXSID: DTXSID7051761
Physical Properties
| Molecular Weight | 124.183 g/mol🔬 EPA CompTox |
| Density | 0.897 g/cm^3🔬 EPA CTX |
| Boiling Point | 190 °C🔬 EPA CTX |
| Melting Point | -5.836 °C📊 OPERA |
| Flash Point | 61.768 °C📊 OPERA |
| Refractive Index | 1.453 Dimensionless📊 OPERA |
| Molar Volume | 144.74 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | 2.139 Log10 unitless📊 OPERA |
| LogD (pH 5.5) | 2.139 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | 2.139 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 4.14 Log10 unitless📊 OPERA |
| Water Solubility | 0.071 mol/L📊 OPERA |
| Henry's Law Constant | 0 atm-m3/mole📊 OPERA |
Transport Properties
| Vapor Pressure | 1.004 mmHg📊 OPERA |
| Surface Tension | 27.578 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 | 2 count💻 Computed |
| Aromatic Rings | 0 count💻 Computed |
| Molar Refractivity | 39.1 cm^3/mol📊 OPERA |
| Polarizability | 15.5 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.
