4-Ethyloctanoic acid (CAS 16493-80-4) — Musky Base Note Fragrance Ingredient
4-Ethyloctanoic acid
CAS 16493-80-4
What Is 4-Ethyloctanoic acid?
4-Ethyloctanoic acid is a synthetic fatty acid used in perfumery to add animalic, musky, or cheesy nuances. It’s found in trace amounts in some dairy products and body odors. This ingredient matters because it provides a primal, sensual depth to fragrances, often used to recreate the scent of human skin or aged cheeses in niche perfumery.
Safety Profile
USE WITH AWARENESSWhat Does 4-Ethyloctanoic acid Smell Like?
4-Ethyloctanoic acid delivers a complex olfactory profile that evolves from sharp, cheesy top notes to a warm, musky heart, finally settling into a sweaty, animalic base. Imagine aged Parmesan meeting unwashed skin – initially repulsive yet strangely compelling. The dry-down is intimate, clinging to skin with a primal persistence that makes it invaluable for fragrances seeking a human touch.
In Famous Fragrances
Fragrance associations may not reflect actual formulations.
Used here to amplify the blood-milk-semen accord, creating one of perfumery’s most controversial scents. The acid provides the sweaty human realism that makes this fragrance so disturbingly evocative.
2D Molecular Structure
SMILES: CCCCC(CC)CCC(O)=O
Chemistry, Properties & Perfumer Guide
The Chemistry
A branched-chain fatty acid (C10H20O2) typically synthesized through hydrocarbon oxidation or malonic ester synthesis. Its potency stems from the ethyl branch at the 4-position, which creates steric hindrance affecting volatility. The molecule’s chirality significantly impacts odor perception, with different enantiomers smelling either intensely cheesy or more subtly musky.
Physical & Chemical Properties
| Molecular Weight | 172.26 g/mol |
|---|---|
| Boiling Point | 272-274 °C |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Niche Perfumery | 0.1-0.5% | Up to 1% | For animalic effects |
| Functional Fragrances | 0.01-0.1% | Up to 0.2% | Cheese flavor enhancement |
Classic Accords
Tip: Always pre-dilute to 1% in alcohol before incorporating into blends.
Alternatives & Comparisons
Less cheesy, more directly sweaty. Used when a cleaner human perspiration effect is desired without dairy notes.
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. Consult current IFRA Standards Library before formulating.
IFRA Status
Not currently restricted by IFRA. Recommended maximum 0.5% in finished products.
EU Allergen Declaration
Not listed as an EU allergen.
GHS Classification
RIFM Assessment
RIFM has not conducted a formal safety assessment on this material.
Sustainability
As a synthetic material, production involves petrochemical feedstocks. Some manufacturers are exploring bio-based synthesis routes using fermented substrates to reduce environmental impact.
Explore 4-Ethyloctanoic acid
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References
- Brenna et al. (2002). Chirality and Odor Perception. Chemical Senses. PubChem CID unavailable
Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Apr 2026.
Report a data errorPhysicochemical Properties
DTXSID: DTXSID40864683
Physical Properties
| Molecular Weight | 172.268 g/mol🔬 EPA CompTox |
| Density | 0.922 g/cm^3📊 OPERA |
| Boiling Point | 268.242 °C📊 OPERA |
| Melting Point | 56.202 °C📊 OPERA |
| Flash Point | 137.16 °C📊 OPERA |
| Refractive Index | 1.442 Dimensionless📊 OPERA |
| Molar Volume | 188.605 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | 3.505 Log10 unitless📊 OPERA |
| LogD (pH 5.5) | 2.991 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | 1.324 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 7.48 Log10 unitless📊 OPERA |
| Water Solubility | 0.002 mol/L📊 OPERA |
| Henry's Law Constant | 0 atm-m3/mole📊 OPERA |
Transport Properties
| Vapor Pressure | 0.001 mmHg📊 OPERA |
| Viscosity | 6.459 cP📊 OPERA |
| Surface Tension | 30.035 dyn/cm📊 OPERA |
| Thermal Conductivity | 143.857 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 | 7 count💻 Computed |
| Aromatic Rings | 0 count💻 Computed |
| Molar Refractivity | 49.901 cm^3/mol📊 OPERA |
| Polarizability | 19.782 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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