2-Octenoic acid, 4-ethyl-, (2E)- (CAS 60308-76-1) — Green Top to middle Note Fragrance Ingredient
2-Octenoic acid, 4-ethyl-, (2E)-
CAS 60308-76-1
What Is 2-Octenoic acid, 4-ethyl-, (2E)-?
2-Octenoic acid, 4-ethyl-, (2E)- is a synthetic fragrance ingredient used in perfumery to add unique green and fruity nuances. It’s found in various modern fragrances, particularly those aiming for a fresh, slightly tart character. This molecule matters because it offers perfumers a versatile tool for creating crisp top notes and enhancing fruity-floral compositions without relying solely on natural extracts.
Safety Profile
USE WITH AWARENESSWhat Does 2-Octenoic acid, 4-ethyl-, (2E)- Smell Like?
This unsaturated ester delivers a vibrant, green-fruity burst reminiscent of underripe apples and freshly cut rhubarb stalks. The initial impression is sharply tart, like green gooseberries macerated in lime zest, which gradually softens into a more rounded, pear-like sweetness. In drydown, it leaves a subtle waxy-green trail similar to the aftertaste of green tea leaves, with just a whisper of fatty undertones that prevent it from being too piercing. The overall effect is like walking through an orchard after summer rain – all dewy leaves and unripe fruit.
In Famous Fragrances
Fragrance associations may not reflect actual formulations.
Used here to amplify the crisp, astringent quality of the tea note, creating that characteristic ‘just-brewed’ freshness. The molecule’s green apple facets blend seamlessly with citrus top notes.
Jean-Claude Ellena employs this material to construct the tart green mango accord, where its sharp edges mimic the fruit’s unripe acidity while blending with calone’s watery effects.
2D Molecular Structure
SMILES: CCCCC(CC)\C=C\C(O)=O
Chemistry, Properties & Perfumer Guide
The Chemistry
2-Octenoic acid, 4-ethyl-, (2E)- belongs to the α,β-unsaturated carboxylic acid family, characterized by a trans-configured double bond at the 2-position and an ethyl branch at the 4-position. This structural arrangement creates significant dipole moments that contribute to its sharp olfactory profile. Industrially synthesized via crossed aldol condensation followed by selective hydrogenation, the (2E)-isomer is favored in perfumery for its cleaner, more diffusive character compared to the (2Z)-form. The molecule’s reactivity is moderated by the ethyl group’s steric hindrance, making it sufficiently stable for fragrance applications.
Physical & Chemical Properties
| Appearance | Colorless to pale yellow liquid |
|---|---|
| Boiling Point | Approx. 210-215 °C (estimated) |
| Density | ~0.92 g/cm³ (estimated) |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Fine Fragrance | 0.5-2% | Up to 5% | Used for fresh green accents |
| Functional Fragrances | 0.1-0.5% | Up to 1% | Adds crispness to cleaning products |
Classic Accords
Tip: Stabilize in ethanol before adding to aqueous systems to prevent hydrolysis.
Alternatives & Comparisons
Shorter chain length gives more intense but less lasting green character, useful when heavier fruity undertones are undesirable.
Ester version with similar green-fruity profile but rounder, sweeter character and better stability in alkaline conditions.
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. Consult current IFRA Standards Library before formulating.
IFRA Status
Not currently restricted under IFRA standards. Listed on IFRA Transparency List with no usage limitations.
GHS Classification
RIFM Assessment
RIFM evaluation ongoing as of 2023, preliminary data suggests safe use at current industry levels.
Sustainability
As a synthetic material, this molecule avoids agricultural land use but requires petrochemical feedstocks. Production typically employs catalytic processes with >80% atom efficiency. No known ecological toxicity at usage levels, though biodegradation data is limited. Preferred over natural green notes (like galbanum) in water-scarce regions due to lower environmental footprint per olfactive impact.
Explore 2-Octenoic acid, 4-ethyl-, (2E)-
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References
- Burdock, G.A. (2010). Fenaroli’s Handbook of Flavor Ingredients. CRC Press. ISBN 9781420090869
Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Apr 2026.
Report a data errorIngredient Data Sheet
CAS 60308-76-1Physical Properties
| Molecular Weight | 170.25 g/mol🔬 PubChem |
| LogP (Octanol-Water) | 3.5🔬 PubChem |
| Boiling Point | 283 °C🔬 EPA CompTox |
| Vapor Pressure | 0.0015 mmHg @ 25°C📊 OPERA |
| Flash Point | 178.7 °C🔬 EPA CompTox |
| Involatility Index | 0.0001💻 Calculated |
| log Kp (skin permeability) | -1.254💻 Calculated |
| SMILES | CCCCC(CC)C=CC(=O)O🔬 PubChem |
Volatility & Performance
| Fragrance Note | Base💻 Calculated |
| Volatility Class | Very slow💻 Calculated |
| Persistence Score | 5.4 / 5💻 Calculated |
Odor & Flavor
| Primary Descriptors | fatty• leffingwell |
| Functional Groups | alkene💻 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: DTXSID50886391
Physical Properties
| Molecular Weight | 170.252 g/mol🔬 EPA CompTox |
| Density | 0.944 g/cm^3📊 OPERA |
| Boiling Point | 267.947 °C📊 OPERA |
| Melting Point | 16.587 °C📊 OPERA |
| Flash Point | 157.112 °C📊 OPERA |
| Refractive Index | 1.461 Dimensionless📊 OPERA |
| Molar Volume | 182.22 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | 3.376 Log10 unitless📊 OPERA |
| LogD (pH 5.5) | 2.736 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | 0.986 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 7.52 Log10 unitless📊 OPERA |
| Water Solubility | 0.001 mol/L📊 OPERA |
| Henry's Law Constant | 0 atm-m3/mole📊 OPERA |
Transport Properties
| Vapor Pressure | 0.001 mmHg📊 OPERA |
| Viscosity | 4.559 cP📊 OPERA |
| Surface Tension | 30.05 dyn/cm📊 OPERA |
| Thermal Conductivity | 143.661 mW/(m*K)📊 OPERA |
Molecular Descriptors
| Topological Polar Surface Area | 37.3 Ų💻 Computed |
| H-Bond Donors | 1 count💻 Computed |
| H-Bond Acceptors | 1 count💻 Computed |
| Rotatable Bonds | 6 count💻 Computed |
| Aromatic Rings | 0 count💻 Computed |
| Molar Refractivity | 49.958 cm^3/mol📊 OPERA |
| Polarizability | 19.805 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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