Methylheptenone (isomer unspecified) (CAS 0409-02-09) — Citrus Top to Middle Note Fragrance Ingredient
Methylheptenone (isomer unspecified)
CAS 0409-02-09
What Is Methylheptenone (isomer unspecified)?
Methylheptenone is a synthetic fragrance molecule used to add fruity, green, and slightly woody notes to perfumes and scented products. You’ll encounter it in fresh citrus colognes, floral bouquets, and some modern woody fragrances. This versatile ingredient matters because it bridges citrus and woody accords, helping perfumers create natural-smelling transitions between top and heart notes. Its subtle complexity enhances freshness without overpowering other ingredients.
Safety Profile
GENERALLY SAFEWhat Does Methylheptenone (isomer unspecified) Smell Like?
Methylheptenone bursts with a vibrant, slightly tart greenness reminiscent of freshly crushed blackcurrant leaves, evolving into a juicy grapefruit-like citrus character. As it settles, the aroma develops a subtle woody backbone akin to young cedar twigs, with a faint metallic edge that adds modern crispness. The dry-down reveals a clean, almost soapy muskiness that lingers close to the skin. This chameleon-like molecule behaves differently in various blends – amplifying citrus in colognes, adding green depth to florals, and providing lift to woody compositions.
In Famous Fragrances
Fragrance associations may not reflect actual formulations.
Used here to enhance the citrus-herbal opening, adding dimension to the bergamot and tying it to the floral heart. The green facets complement the rosemary while the woody undertones bridge to the oakmoss base.
Provides the initial crisp green sparkle that makes the violet leaf accord smell freshly crushed rather than flat, while its woody side harmonizes with the sandalwood base.
Contributes to the sun-warmed fig leaf illusion, blending with citrus notes for freshness while its woody aspects ground the green accord in the Mediterranean landscape.
Used in the mojito accord to add authentic lime leaf realism, its green facets enhancing the mint while the woody side connects to the woody-amber drydown.
Helps create the dewy citrus opening by adding dimensionality to the lemon, making it smell more like a whole fruit rather than just peel, while supporting the floral heart.
Chemistry, Properties & Perfumer Guide
The Chemistry
Methylheptenone belongs to the unsaturated ketone class, specifically a methylated heptenone. While it can occur naturally in trace amounts in some essential oils, commercial versions are synthesized through base-catalyzed condensation of acetone with pentanal or via oxidation of corresponding alcohols. The most common isomer in perfumery is 6-methyl-5-hepten-2-one, which has optimal olfactory properties. The molecule’s reactivity comes from its conjugated double bond system and ketone functionality, making it useful for further chemical modifications in fragrance synthesis.
Physical & Chemical Properties
| Boiling Point | 173-175 °C |
|---|---|
| Density | 0.855 g/cm³ |
| Refractive Index | 1.442 |
| Flash Point | 62 °C |
| Solubility | Slightly soluble in water, soluble in alcohol and oils |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Fine Fragrance | 0.5-2% | Up to 5% | Fresh top notes and green accords |
| Functional Fragrance | 0.1-0.5% | Up to 1% | Soap and detergent freshness |
| Flavor | 1-10 ppm | Up to 20 ppm | Citrus and tropical fruit flavors |
Classic Accords
Tip: Use at 0.5-1% in citrus tops to prevent flatness, adding before citral to allow proper blending.
Alternatives & Comparisons
The most common isomer with sharper green character, preferred when more citrus lift is needed in the formula.
From tagetes oil, offers similar green-fruity profile but with more floral depth and less woody character.
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. Consult current IFRA Standards Library before formulating.
IFRA Status
No restrictions under IFRA standards. Listed in IFRA Transparency List with no usage limitations.
GHS Classification
RIFM Assessment
Evaluated by RIFM and considered safe for current usage levels in fragrances.
Sustainability
As a synthetic material, methylheptenone has minimal environmental impact in production compared to natural equivalents. The synthesis from acetone and pentanal is atom-efficient with few byproducts. Being produced in controlled facilities reduces variability and ensures consistent quality without seasonal fluctuations. The molecule’s potency means very small quantities are needed in formulations, reducing overall chemical load in finished products.
Explore Methylheptenone (isomer unspecified)
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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.
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