Isovaleric acid (CAS 503-74-2) — Musky Heart to base Note Fragrance Ingredient
Isovaleric acid
CAS 503-74-2
What Is Isovaleric acid?
Isovaleric acid is a sharp, pungent organic acid that occurs naturally in some cheeses, sweat, and valerian root. Most people encounter it as part of fermented foods or as a minor component in certain perfumes. Though intense on its own, it adds animalic depth when carefully blended and diluted in fragrances.
Safety Profile
USE WITH AWARENESSWhat Does Isovaleric acid Smell Like?
Isovaleric acid assaults the nose with an intensely cheesy, sweaty odor that evokes aged dairy and locker rooms. Undiluted, it’s nearly unbearable—like concentrated body odor with sour milk undertones. When properly diluted in alcohol, it transforms into a complex animalic musk with leathery facets. The dry-down reveals subtle fruity nuances reminiscent of overripe tropical fruit, making it surprisingly versatile in trace amounts for adding primal depth to chypres and leather accords.
In Famous Fragrances
Fragrance associations may not reflect actual formulations.
Used in minute quantities to create the controversial ‘human sweat’ facet that makes this leather fragrance so animalic and provocative.
Provides a raw, untamed edge to the herbal-leather composition, enhancing its primal forest character.
2D Molecular Structure
SMILES: CC(C)CC(O)=O
Chemistry, Properties & Perfumer Guide
The Chemistry
Isovaleric acid (3-methylbutanoic acid) is a branched short-chain fatty acid. Industrially produced via oxidation of isovaleraldehyde or fermentation. Its potency stems from the carboxyl group’s hydrogen bonding with olfactory receptors. The branched methyl group increases volatility compared to straight-chain acids. No chiral centers in this molecule, but its odor detection threshold is exceptionally low at 0.2 ppb in air.
Physical & Chemical Properties
| Boiling Point | 176 °C |
|---|---|
| Density | 0.925 g/cm³ |
| Vapor Pressure | 0.3 mmHg at 25°C |
| Solubility | 25 g/L in water |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Fine Fragrance | 0.01-0.1% | Up to 0.3% | Extremely powerful modifier |
| Functional Fragrance | 0.001-0.01% | Up to 0.05% | Masking agent for malodors |
| Flavoring | 5-50 ppm | Up to 100 ppm | Cheese and dairy flavors |
Classic Accords
Tip: Always pre-dilute to 1% or lower in alcohol before adding to blends—undiluted will overwhelm compositions.
Alternatives & Comparisons
Straight-chain version with similar but less complex odor profile, useful when less animalic character is desired.
Slightly sweeter and fruitier alternative that maintains some cheesy character without the intense sweat aspect.
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. Consult current IFRA Standards Library before formulating.
IFRA Status
No IFRA restrictions. Classified as a carboxylic acid without specific usage limits.
GHS Classification
RIFM Assessment
RIFM evaluation confirms safe use at current industry levels, with skin irritation being the primary concern at high concentrations.
Sustainability
Primarily synthesized from petrochemical precursors, though some natural derivation from valerian root exists. Production is energy-intensive but requires minimal quantities due to extreme potency. No known ecological toxicity at fragrance usage levels, but proper waste handling is crucial due to acidity.
Explore Isovaleric acid
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References
- PubChem Compound Summary for Isovaleric acid PubChem CID 10430
- Brenna et al. (2002). Odor detection thresholds of branched esters. Chemical Senses. DOI:10.1093/chemse/27.8.693
Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Apr 2026.
Report a data errorPerfumer’s Notes
FEMA #: 3102 | IOFI #: Nature Identical
Isovaleric acid has a characteristic disagreeable, rancid, cheese-like odor. It is extremely penetrating and persistent with a sour taste. May consist of one or a mixture of isomers or n-pentanoic acid and/or 2- or 3-methyl butanoic acid.
Odor: [‘cheesy’, ‘fruity’, ‘sour’]
MW: 102.13
LogP: 1.2
Ingredient Data Sheet
CAS 503-74-2Physical Properties
| Molecular Weight | 102.13 g/mol🔬 PubChem |
| LogP (Octanol-Water) | 1.2🔬 PubChem |
| Boiling Point | 176.5 °C🔬 EPA CompTox |
| Vapor Pressure | 0.44 mmHg @ 25°C📊 OPERA |
| Flash Point | 70 °C🔬 EPA CompTox |
| Involatility Index | 0.0469💻 Calculated |
| log Kp (skin permeability) | -2.471💻 Calculated |
| SMILES | CC(C)CC(=O)O🔬 PubChem |
Volatility & Performance
| Fragrance Note | Top💻 Calculated |
| Volatility Class | Slow💻 Calculated |
| Persistence Score | 0.5 / 5💻 Calculated |
Odor & Flavor
| Primary Descriptors | fruity• leffingwell |
| “power of the odor, give impression of considerable tenacity. In extreme dilution the odor becomes more agreeable, herbaceous, more dry than the odor of the n-Valeric acid.”📖 Arctander | |
| Isovaleric acid has a characteristic disagreeable, rancid, cheese-like odor. It is extremely penetrating and persistent with a sour taste. May consist of one or a mixture of isomers or n-pentanoic acid and/or 2- or 3-methyl butanoic acid.📖 Fenaroli | |
Flavor Notes (Arctander)
| “It finds some use in flavor compositions, generally for the same purposes as mentioned under n-Valeric acid, except that the iso-Valeric acid is more useful in Nut and Coffee imitations due to its peculiar warm-herbaceous taste in concentrations lower than 20 ppm.”📖 Arctander |
Sensory Thresholds
| Odor Detection Threshold | 0.7092 ppm (n=38)📖 van Gemert |
Regulatory Status
| FEMA Number | FEMA 3102⚖️ 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: DTXSID5029182
Physical Properties
| Molecular Weight | 102.133 g/mol🔬 EPA CompTox |
| Density | 0.927 g/cm^3🔬 EPA CTX |
| Boiling Point | 176.7 °C🔬 EPA CTX |
| Melting Point | -30.779 °C🔬 EPA CTX |
| Flash Point | 73.421 °C🔬 EPA CTX |
| Refractive Index | 1.418 Dimensionless📊 OPERA |
| Molar Volume | 106.072 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | 5.275 Log10 unitless🔬 EPA CTX |
| LogD (pH 5.5) | 0.337 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | -1.476 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 4.19 Log10 unitless📊 OPERA |
| Water Solubility | 0.422 mol/L🔬 EPA CTX |
| Henry's Law Constant | 0 atm-m3/mole🔬 EPA CTX |
Transport Properties
| Vapor Pressure | 0.495 mmHg🔬 EPA CTX |
| Viscosity | 2.244 cP📊 OPERA |
| Surface Tension | 28.319 dyn/cm📊 OPERA |
| Thermal Conductivity | 140.07 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 | 2 count💻 Computed |
| Aromatic Rings | 0 count💻 Computed |
| Molar Refractivity | 26.736 cm^3/mol📊 OPERA |
| Polarizability | 10.599 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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