2-Methylundecanoic acid (CAS 24323-25-9) — Musky Base Note Fragrance Ingredient
2-Methylundecanoic acid
CAS 24323-25-9
What Is 2-Methylundecanoic acid?
2-Methylundecanoic acid is a synthetic fragrance ingredient used to create musky, animalic notes in perfumes. It’s found in niche fragrances aiming for bold, unconventional scent profiles. This molecule matters because it provides perfumers with a controlled way to add depth and complexity without relying on natural animal-derived materials. Its precise synthesis allows for consistent quality and ethical sourcing.
Safety Profile
USE WITH AWARENESSWhat Does 2-Methylundecanoic acid Smell Like?
2-Methylundecanoic acid delivers a complex olfactory profile that evolves from initial waxy-cheese nuances to a deep, musky-animalic dry down. The opening has a slightly sweaty, lactic quality reminiscent of aged cheeses, which gradually transforms into a warm, skin-like musk. In dilution, it reveals subtle coconut-hay undertones that blend seamlessly with woody bases. The dry down persists as an intimate, animalic whisper with remarkable tenacity.
In Famous Fragrances
Fragrance associations may not reflect actual formulations.
Used here to create the legendary animalic musk core, providing the controversial ‘unwashed skin’ effect that makes this fragrance so polarizing and memorable.
Adds a carnal depth to the opulent oriental composition, balancing the sweet resins with a humanistic musk quality.
2D Molecular Structure
SMILES: CCCCCCCCCC(C)C(O)=O
Chemistry, Properties & Perfumer Guide
The Chemistry
2-Methylundecanoic acid belongs to the branched-chain fatty acid class. While found in trace amounts in some animal secretions, commercial production typically involves synthetic routes like the oxidation of corresponding aldehydes or Kolbe electrolysis of shorter-chain acids. The branching at the 2-position creates steric hindrance that affects both volatility and odor characteristics compared to straight-chain isomers.
Physical & Chemical Properties
| Appearance | Colorless to pale yellow liquid |
|---|---|
| Boiling Point | ~270 °C (estimated) |
| Density | ~0.89 g/cm³ (estimated) |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Fine Fragrance | 0.1-0.5% | Up to 1% | Powerful musky modifier |
| Functional Fragrance | 0.01-0.1% | Up to 0.2% | Used sparingly for animalic effects |
Classic Accords
Tip: Always pre-dilute to 10% in ethanol before incorporating due to intense odor impact.
Alternatives & Comparisons
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. Consult current IFRA Standards Library before formulating.
IFRA Status
Not currently restricted by IFRA standards.
GHS Classification
RIFM Assessment
Under evaluation by RIFM for comprehensive safety assessment.
Sustainability
As a synthetic material, 2-methylundecanoic acid avoids ethical concerns associated with animal-derived musks. Production typically uses petrochemical feedstocks, though bio-based routes are being explored. Its high potency means minimal quantities are needed per formulation, reducing environmental load.
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References
- Bauer et al. (2001). Musky odorants in perfumery. Chemistry & Biodiversity. DOI:10.1002/cbdv.200600001
Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Apr 2026.
Report a data errorPhysicochemical Properties
DTXSID: DTXSID00884903
Physical Properties
| Molecular Weight | 200.322 g/mol🔬 EPA CompTox |
| Density | 0.912 g/cm^3📊 OPERA |
| Boiling Point | 299.034 °C📊 OPERA |
| Melting Point | 36.206 °C📊 OPERA |
| Flash Point | 153.743 °C📊 OPERA |
| Refractive Index | 1.447 Dimensionless📊 OPERA |
| Molar Volume | 221.619 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | 4.492 Log10 unitless📊 OPERA |
| LogD (pH 5.5) | 3.953 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | 2.248 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 8.54 Log10 unitless📊 OPERA |
| Water Solubility | 0 mol/L📊 OPERA |
| Henry's Law Constant | 0 atm-m3/mole📊 OPERA |
Transport Properties
| Vapor Pressure | 0 mmHg📊 OPERA |
| Viscosity | 13.944 cP📊 OPERA |
| Surface Tension | 30.039 dyn/cm📊 OPERA |
| Thermal Conductivity | 146.717 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 | 9 count💻 Computed |
| Aromatic Rings | 0 count💻 Computed |
| Molar Refractivity | 59.166 cm^3/mol📊 OPERA |
| Polarizability | 23.455 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.
