3-Hexenoic acid (CAS 4219-24-3) — Green Top to middle Note Fragrance Ingredient
3-Hexenoic acid
CAS 4219-24-3
What Is 3-Hexenoic acid?
3-Hexenoic acid is a synthetic fragrance ingredient with a green, leafy aroma. It’s primarily used in perfumery to create fresh, outdoorsy scents. This compound matters because it adds realistic ‘cut grass’ or unripe fruit nuances that are difficult to achieve with natural extracts alone.
Safety Profile
GENERALLY SAFEWhat Does 3-Hexenoic acid Smell Like?
3-Hexenoic acid bursts with an intensely green, vegetative character reminiscent of freshly crushed leaves and unripe bananas. The sharp top note evolves into a more rounded, fatty-green heart with subtle tropical fruit undertones. In drydown, it leaves a clean, slightly waxy trail that blends well with citrus and floral notes. The overall effect is like walking through a greenhouse after watering – damp, alive, and chlorophyll-rich.
2D Molecular Structure
SMILES: CCC=CCC(O)=O
Chemistry, Properties & Perfumer Guide
The Chemistry
3-Hexenoic acid is an unsaturated fatty acid derivative belonging to the aliphatic carboxylic acid family. It exists as both cis and trans isomers, with the cis-3 form being more commonly used in perfumery for its superior green character. Industrially produced through controlled oxidation of hexenols or via specialized fermentation processes, this molecule lacks significant natural sources. The double bond at position 3 creates its distinctive reactive nature and contributes to the fresh-cut vegetative odor profile.
Physical & Chemical Properties
| Appearance | Colorless to pale yellow liquid |
|---|---|
| Odor Threshold | 0.1 ppm in water |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Fine Fragrance | 0.1-0.5% | Up to 1% | Green modifier |
| Functional Fragrance | 0.05-0.2% | Up to 0.5% | Freshness booster |
| Flavor | 1-5 ppm | Up to 10 ppm | Unripe fruit nuance |
Classic Accords
Tip: Stabilize in ethanol before adding to water-based formulations to prevent esterification.
Alternatives & Comparisons
More floral-green with less fatty character, preferred for delicate compositions requiring lighter green notes.
Stronger cheese-like undertones, used when more animalic green notes are desired.
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. Consult current IFRA Standards Library before formulating.
IFRA Status
No current restrictions under IFRA standards.
RIFM Assessment
RIFM has reviewed this material and found it safe at current usage levels.
Sustainability
As a synthetic material, 3-hexenoic acid has minimal environmental impact in production compared to natural alternatives requiring agricultural land. Modern synthesis routes use renewable feedstocks where possible. Being highly potent, it requires minimal quantities in formulations, reducing overall carbon footprint per kilo of finished fragrance.
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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.
Report a data errorPhysicochemical Properties
DTXSID: DTXSID5063362
Physical Properties
| Molecular Weight | 114.144 g/mol🔬 EPA CompTox |
| Density | 0.965 g/cm^3🔬 EPA CTX |
| Boiling Point | 208 °C🔬 EPA CTX |
| Melting Point | 12 °C🔬 EPA CTX |
| Flash Point | 99.051 °C📊 OPERA |
| Refractive Index | 1.456 Dimensionless📊 OPERA |
| Molar Volume | 115.816 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | 1.403 Log10 unitless📊 OPERA |
| LogD (pH 5.5) | -0.119 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | -1.971 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 4.77 Log10 unitless📊 OPERA |
| Water Solubility | 0.128 mol/L📊 OPERA |
| Henry's Law Constant | 0 atm-m3/mole📊 OPERA |
Transport Properties
| Vapor Pressure | 0.104 mmHg📊 OPERA |
| Viscosity | 2.73 cP📊 OPERA |
| Surface Tension | 30.318 dyn/cm📊 OPERA |
| Thermal Conductivity | 147.555 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 | 3 count💻 Computed |
| Aromatic Rings | 0 count💻 Computed |
| Molar Refractivity | 31.468 cm^3/mol📊 OPERA |
| Polarizability | 12.475 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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