2-Hexenal (CAS 505-57-7) — Green Top Note Fragrance Ingredient
2-Hexenal
CAS 505-57-7
What Is 2-Hexenal?
2-Hexenal is a green, leafy-smelling compound used in perfumes and flavorings. You might encounter it in fresh-cut grass scents or cucumber-melon body products. This ingredient matters because it creates ultra-realistic green notes, helping perfumers replicate nature’s crispness without harvesting plants.
Safety Profile
USE WITH AWARENESSWhat Does 2-Hexenal Smell Like?
2-Hexenal bursts with the piercing greenness of freshly crushed tomato leaves or snapped pea pods. Its sharp top note evolves into wet cucumber skins and unripe bananas, leaving a faintly waxy, vegetal trail. The dry-down reveals why perfumers call it ‘nature’s green aldehyde’ – a clean, slightly metallic freshness lingers like morning dew on cut stems.
In Famous Fragrances
Fragrance associations may not reflect actual formulations.
Used here to amplify the hyper-realistic galbanum opening, creating one of perfumery’s most iconic green accords. The 2-hexenal adds a ‘just-cut’ vegetal sharpness that makes the composition smell alive.
Provides the startling wet melon rind effect in this monsoon garden fantasy, blending with calone to create an aqueous green illusion.
2D Molecular Structure
SMILES: CCCC=CC=O
Chemistry, Properties & Perfumer Guide
The Chemistry
2-Hexenal is an α,β-unsaturated aldehyde with the molecular formula C6H10O. As (E)-2-hexenal (trans isomer), it’s the major component of ‘leaf alcohol’ released when plants are damaged. Industrially produced via oxidation of 1-hexanol or aldol condensation of acetaldehyde with butanal. The cis isomer (leaf aldehyde) occurs naturally but is less stable. Its electrophilic β-carbon makes it reactive with nucleophiles like thiols – the basis of both its olfactory impact and skin sensitization potential.
Physical & Chemical Properties
| Boiling Point | 131-132 °C |
|---|---|
| Density | 0.849 g/cm³ |
| Refractive Index | 1.426 |
| Flash Point | 26 °C |
| Vapor Pressure | 10.5 mmHg |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Fine Fragrance | 0.1-0.5% | Up to 1% | Green top note accent |
| Functional Fragrance | 0.05-0.2% | Up to 0.5% | Freshness booster |
| Flavor | 1-5 ppm | Up to 10 ppm | Green apple/cucumber note |
Classic Accords
Tip: Stabilize in ethanol solutions below 1% to prevent polymerization over time.
Alternatives & Comparisons
Less sharp, more rounded green note with better stability. Use when a gentler leafy effect is desired.
Milder aldehyde character without the green punch. Suitable for softer green applications.
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. Consult current IFRA Standards Library before formulating.
IFRA Status
No IFRA restrictions. Listed on 49th Amendment as safe at current usage levels.
EU Allergen Declaration
Not listed as EU allergen.
GHS Classification
RIFM Assessment
RIFM evaluation confirms safe use at current industry levels with proper handling precautions.
Sustainability
While naturally occurring, commercial 2-hexenal is synthesized from petrochemical feedstocks. Green chemistry routes using bio-based hexanol are being developed. Its high potency means minimal quantities are needed, reducing environmental load compared to some natural green materials.
Explore 2-Hexenal
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References
- Burdock, G.A. (2010). Fenaroli’s Handbook of Flavor Ingredients. CRC Press.
- Sell, C. (2006). The Chemistry of Fragrances. RSC Publishing.
Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Apr 2026.
Report a data errorIngredient Data Sheet
CAS 505-57-7Physical Properties
| Molecular Weight | 98.14 g/mol🔬 PubChem |
| LogP (Octanol-Water) | 1.5🔬 PubChem |
| Boiling Point | 47 °C🔬 EPA CompTox |
| Vapor Pressure | 6.6 mmHg @ 25°C📊 OPERA |
| Involatility Index | 0.718💻 Calculated |
| log Kp (skin permeability) | -2.234💻 Calculated |
Volatility & Performance
| Fragrance Note | Top💻 Calculated |
| Volatility Class | Moderate💻 Calculated |
| Persistence Score | 0.5 / 5💻 Calculated |
Odor & Flavor
| 2-Hexenal has a sweet, fragrant, almond, fruity green, leafy, apple, plum, vegetable odor.📖 Fenaroli |
Sensory Thresholds
| Odor Detection Threshold | 0.1597 ppm (n=2)📖 van Gemert |
Regulatory Status
| IFRA Listed | Yes — see IFRA Standards for category limits⚖️ IFRA 51 |
| IOFI Classification | Nature Identical📖 Fenaroli |
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: DTXSID7021609
Physical Properties
| Molecular Weight | 98.145 g/mol🔬 EPA CompTox |
| Density | 0.845 g/cm^3🔬 EPA CTX |
| Boiling Point | 141.057 °C📊 OPERA |
| Melting Point | -37.623 °C📊 OPERA |
| Flash Point | 42.422 °C📊 OPERA |
| Refractive Index | 1.422 Dimensionless📊 OPERA |
| Molar Volume | 118.509 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | 1.139 Log10 unitless📊 OPERA |
| LogD (pH 5.5) | 1.139 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | 1.139 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 3.65 Log10 unitless📊 OPERA |
| Water Solubility | 0.074 mol/L📊 OPERA |
| Henry's Law Constant | 0 atm-m3/mole🔬 EPA CTX |
Transport Properties
| Vapor Pressure | 6.6 mmHg🔬 EPA CTX |
| Viscosity | 0.607 cP📊 OPERA |
| Surface Tension | 24.845 dyn/cm📊 OPERA |
| Thermal Conductivity | 145.745 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 | 3 count💻 Computed |
| Aromatic Rings | 0 count💻 Computed |
| Molar Refractivity | 30.091 cm^3/mol📊 OPERA |
| Polarizability | 11.929 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.
