Hexanal (CAS 66-25-1) — Green Top Note Fragrance Ingredient
Hexanal
CAS 66-25-1
What Is Hexanal?
Hexanal is a synthetic aroma chemical that gives off a fresh, green, grassy scent. You’ll encounter it in products like air fresheners and cleaning supplies where a crisp, outdoor-like quality is desired. This molecule matters because it’s one of the key building blocks for creating natural-smelling green and cut-grass accords without using actual plant extracts.
Safety Profile
GENERALLY SAFEWhat Does Hexanal Smell Like?
Hexanal bursts with the vibrant intensity of freshly cut grass – imagine the first lawn mow of spring. Its top note is sharply green, almost waxy like the broken stems of tomato plants, evolving into a cleaner, more cucumber-like freshness. The dry-down reveals a faint nutty undertone, like the husks of unripe almonds, before fading completely. This molecule is all about that fleeting moment of vegetal rupture, never lingering too long but making an unforgettable first impression.
In Famous Fragrances
Fragrance associations may not reflect actual formulations.
Hexanal provides the photorealistic wet vegetation effect in this monsoonal garden fantasy, pairing with calone for dewy melon nuances.
Used sparingly here to enhance the naturalistic grassy top notes alongside violet leaf, creating an aristocratic lawn effect.
The reformulation employs hexanal to reconstruct the iconic green galbanum burst of the original composition.
2D Molecular Structure
SMILES: CCCCCC=O
Chemistry, Properties & Perfumer Guide
The Chemistry
Hexanal (C6H12O) is a straight-chain aliphatic aldehyde, the six-carbon member of the homologous series. Industrially produced via hydroformylation of 1-pentene or oxidation of hexanol. Lacks chiral centers but exists in equilibrium with its cyclic hemiactal form in solution. Shows typical aldehyde reactivity including facile oxidation to hexanoic acid and propensity for aldol condensation reactions at elevated pH.
Physical & Chemical Properties
| Boiling Point | 131 °C |
|---|---|
| Density | 0.814 g/cm³ |
| Vapor Pressure | 10.5 mmHg at 25°C |
| Flash Point | 32 °C |
| Solubility | Slightly soluble in water, miscible with organic solvents |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Fine Fragrance | 0.1-0.5% | Up to 1% | Used for fresh top notes |
| Functional Fragrance | 0.5-2% | Up to 5% | Cleaning product freshnes |
| Flavor | 1-10 ppm | Up to 20 ppm | Green apple/fruit nuances |
Classic Accords
Tip: Stabilize with 0.1% BHT to prevent oxidation during storage.
Alternatives & Comparisons
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. Consult current IFRA Standards Library before formulating.
IFRA Status
Not restricted under current IFRA standards (Amendment 49).
GHS Classification
RIFM Assessment
RIFM assessment confirms safe use at current industry levels (FEMA GRAS 2557).
Sustainability
Synthesized from petrochemical feedstocks but with relatively low environmental impact due to efficient catalytic processes. No known ecological toxicity concerns at usage levels. Preferred over natural isolates (e.g. from grasses) which require large-scale biomass processing.
Explore Hexanal
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References
- Burdock, G.A. (2010). Fenaroli’s Handbook of Flavor Ingredients. CRC Press. ISBN 9781439852179
- IFRA Standards Library (2021). Amendment 49. IFRA Standards
- PubChem Compound Summary for Hexanal CID 6184
Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Apr 2026.
Report a data errorPerfumer’s Notes
FEMA #: 2557 | IOFI #: Nature Identical
Hexanal has a fatty, green, grassy, powerful, penetrating characteristic fruity odor and taste (on dilution).
Odor: [‘fatty’, ‘fruity’, ‘grassy’, ‘green’]
MW: 100.16
LogP: 1.8
Ingredient Data Sheet
CAS 66-25-1Physical Properties
| Molecular Weight | 100.16 g/mol🔬 PubChem |
| LogP (Octanol-Water) | 1.8🔬 PubChem |
| Boiling Point | 127.8 °C🔬 EPA CompTox |
| Vapor Pressure | 11.3 mmHg @ 25°C📊 OPERA |
| Flash Point | 32.2 °C🔬 EPA CompTox |
| Involatility Index | 1.2169💻 Calculated |
| log Kp (skin permeability) | -2.033💻 Calculated |
| SMILES | CCCCCC=O🔬 PubChem |
Volatility & Performance
| Fragrance Note | Top💻 Calculated |
| Volatility Class | Fast💻 Calculated |
| Persistence Score | 0.5 / 5💻 Calculated |
Odor & Flavor
| Primary Descriptors | fattyfruitygrassygreen• leffingwell |
| Functional Groups | aldehyde💻 RDKit |
| “This aldehyde is occasionally used – in very discrete amounts – in perfumes as part of a top-note complex, or in the reproduction of artificial essential oils, etc. As a "green" odor, it does not give the naturalness or beauty of the unsaturated aldehydes and the corresponding alcohols and esters, but it has some advantage in a very low cost, making it useful in masking odors for industrial purposes, etc.”📖 Arctander | |
| Hexanal has a fatty, green, grassy, powerful, penetrating characteristic fruity odor and taste (on dilution).📖 Fenaroli | |
Flavor Notes (Arctander)
| “It is used more commonly in flavor compositions for imitation Butter, Cheese, Honey, Rum, Arak, etc. and in many fruit complexes. The concentration is normally mere traces, e. g. 1 to 5 ppm in the finished product.”📖 Arctander |
Sensory Thresholds
| Odor Detection Threshold | 0.3649 ppm (n=32)📖 van Gemert |
Regulatory Status
| FEMA Number | FEMA 2557⚖️ FEMA GRAS |
| GRAS Status | Generally Recognized as Safe⚖️ FEMA GRAS |
| 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: DTXSID2021604
Physical Properties
| Molecular Weight | 100.161 g/mol🔬 EPA CompTox |
| Density | 1.496 g/cm^3🔬 EPA CTX |
| Boiling Point | 129.96 °C🔬 EPA CTX |
| Melting Point | -51.455 °C🔬 EPA CTX |
| Flash Point | 7.606 °C🔬 EPA CTX |
| Refractive Index | 1.396 Dimensionless📊 OPERA |
| Molar Volume | 124.895 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | 1.817 Log10 unitless🔬 EPA CTX |
| LogD (pH 5.5) | 1.951 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | 1.951 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 4.41 Log10 unitless🔬 EPA CTX |
| Water Solubility | 0.051 mol/L🔬 EPA CTX |
| Henry's Law Constant | 0 atm-m3/mole🔬 EPA CTX |
Transport Properties
| Vapor Pressure | 12.238 mmHg🔬 EPA CTX |
| Viscosity | 0.739 cP📊 OPERA |
| Surface Tension | 24.813 dyn/cm📊 OPERA |
| Thermal Conductivity | 140.023 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 | 30.033 cm^3/mol📊 OPERA |
| Polarizability | 11.906 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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