2-trans-6-trans-Octadienal (CAS 56767-18-1) — Green Top Note Fragrance Ingredient
2-trans-6-trans-Octadienal
CAS 56767-18-1
What Is 2-trans-6-trans-Octadienal?
2-trans-6-trans-Octadienal is a synthetic aroma chemical prized by perfumers for its intensely green, cucumber-like character. While not found in consumer products directly, it’s a key building block in creating fresh, vegetal accords in modern fragrances. This aldehyde matters because it delivers hyper-realistic ‘just-cut’ green notes that can’t be replicated by natural materials alone.
Safety Profile
USE WITH AWARENESSWhat Does 2-trans-6-trans-Octadienal Smell Like?
This aldehyde explodes with the piercing greenness of crushed cucumber skins and freshly snapped pea pods, underscored by a marine-like brine that makes it remarkably diffusive. The top note is almost violently vegetal – think chlorophyll concentrate with the watery crispness of iceberg lettuce. As it evolves, the heart reveals a softer melon rind character, while the dry-down leaves a whisper of ozone-like freshness. Used at trace levels, it creates the illusion of dewy morning gardens; overdosed, it can dominate compositions with its sappy intensity.
In Famous Fragrances
Fragrance associations may not reflect actual formulations.
Jean-Claude Ellena employs this aldehyde to craft the illusion of rain-drenched vegetation, where its cucumber-water freshness blends with cardamom and ginger for an aqueous tropical effect.
One of the first green chypres to utilize this material, creating the iconic ‘tomato leaf’ accord that defines this groundbreaking vegetal fragrance.
2D Molecular Structure
SMILES: C\C=C\CC\C=C\C=O
Chemistry, Properties & Perfumer Guide
The Chemistry
2-trans-6-trans-Octadienal is an unsaturated aliphatic aldehyde with conjugated double bonds at positions 2 and 6. This structural feature is responsible for its extreme reactivity and powerful odor impact. Industrially synthesized through controlled oxidation of corresponding alcohols or via aldol condensation reactions, the trans-trans isomer is favored for perfumery due to its superior olfactory properties. The molecule’s electrophilic nature makes it prone to polymerization, requiring stabilization with antioxidants in commercial preparations.
Physical & Chemical Properties
| Appearance | Colorless to pale yellow liquid |
|---|---|
| Boiling Point | ~80 °C at 1 mmHg (estimated) |
| Flash Point | >100 °C |
| Solubility | Sparingly soluble in water, miscible with ethanol and oils |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Fine Fragrance | 0.01-0.1% | Up to 0.3% | Used at trace levels for lift and diffusion |
| Functional Fragrance | 0.001-0.01% | Up to 0.05% | Provides fresh top notes in detergents |
| Flavors | 0.1-1 ppm | Up to 5 ppm | Cucumber/melon flavor enhancer |
Classic Accords
Tip: Always pre-dilute to 1% or lower before incorporation – the raw material can overwhelm blends.
Alternatives & Comparisons
More grass-like and less marine, this shorter-chain aldehyde offers similar green impact without the cucumber nuance.
A synthetic green with better stability, though lacking the watery freshness of octadienal.
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. Consult current IFRA Standards Library before formulating.
IFRA Status
No specific restrictions under IFRA 51st Amendment. General aldehyde precautions apply.
EU Allergen Declaration
Not listed in EU allergen regulation (EC) No 1223/2009.
GHS Classification
RIFM Assessment
RIFM evaluation pending. Limited data suggests moderate skin sensitization potential at high concentrations.
Sustainability
As a purely synthetic material, 2-trans-6-trans-Octadienal avoids agricultural land use but requires petrochemical feedstocks. Production typically involves platinum-catalyzed reactions with relatively high energy inputs. Recent advances aim to bio-synthesize similar molecules via engineered yeast strains, though commercial viability remains unproven.
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References
- Burdock, G.A. (2010). Fenaroli’s Handbook of Flavor Ingredients. CRC Press. ISBN 9781420090869
- Arctander, S. (1969). Perfume and Flavor Chemicals. Allured Publishing. OCLC 22350
Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Apr 2026.
Report a data errorPhysicochemical Properties
DTXSID: DTXSID70886151
Physical Properties
| Molecular Weight | 124.183 g/mol🔬 EPA CompTox |
| Density | 0.867 g/cm^3📊 OPERA |
| Boiling Point | 194.528 °C📊 OPERA |
| Melting Point | 17.506 °C📊 OPERA |
| Flash Point | 71.782 °C📊 OPERA |
| Refractive Index | 1.455 Dimensionless📊 OPERA |
| Molar Volume | 145.137 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | 2.092 Log10 unitless📊 OPERA |
| LogD (pH 5.5) | 2.092 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | 2.092 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 4.49 Log10 unitless📊 OPERA |
| Water Solubility | 0.017 mol/L📊 OPERA |
| Henry's Law Constant | 0 atm-m3/mole📊 OPERA |
Transport Properties
| Vapor Pressure | 0.662 mmHg📊 OPERA |
| Viscosity | 0.941 cP📊 OPERA |
| Surface Tension | 25.719 dyn/cm📊 OPERA |
| Thermal Conductivity | 146.124 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 | 4 count💻 Computed |
| Aromatic Rings | 0 count💻 Computed |
| Molar Refractivity | 39.414 cm^3/mol📊 OPERA |
| Polarizability | 15.625 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.
