Butyric acid (CAS 107-92-6) — Musky Base Note Fragrance Ingredient
Butyric acid
CAS 107-92-6
What Is Butyric acid?
Butyric acid is a short-chain fatty acid found naturally in rancid butter, parmesan cheese, and human sweat. It’s also synthesized for use in food flavorings and some perfumes. While its pure form smells intensely unpleasant (like vomit), carefully controlled amounts can add dairy-like depth to fragrances, especially when blended with sweeter ingredients.
Safety Profile
USE WITH AWARENESSWhat Does Butyric acid Smell Like?
Pure butyric acid assaults the nose with a piercing, acrid sourness reminiscent of spoiled milk, vomit, and locker room sweat. Yet when diluted below 0.1%, it transforms – adding a creamy, slightly cheesy nuance that enhances dairy accords. In perfumery, it behaves like a volatile chemical chameleon: initially repulsive, then evolving into a warm, animalic base that boosts the richness of vanilla, coconut, and tropical fruit notes. The dry-down leaves a faint fermented butter sensation, making it invaluable for creating authentic dairy or body-odor realism in niche compositions.
In Famous Fragrances
Fragrance associations may not reflect actual formulations.
Uses butyric acid’s sweaty edge to amplify the blood-iron accord, creating a visceral, corporeal fragrance that walks the line between repulsion and fascination.
2D Molecular Structure
SMILES: CCCC(O)=O
Chemistry, Properties & Perfumer Guide
The Chemistry
Butyric acid (C4H8O2) is the simplest fatty acid that retains enough carbon atoms to exhibit both hydrophilic and hydrophobic properties. Industrially produced via oxidation of butyraldehyde or fermentation by anaerobic bacteria like Clostridium butyricum. Its volatility stems from the short 4-carbon chain, while the carboxyl group gives it water solubility. Exists as two enantiomers, though most commercial forms are racemic mixtures. Key to its olfactory impact is the molecule’s ability to bind strongly to human olfactory receptors tuned to detect rancidity.
Physical & Chemical Properties
| Boiling Point | 163.5 °C |
|---|---|
| Density | 0.96 g/cm³ |
| Vapor Pressure | 0.43 mmHg at 25°C |
| Solubility | Miscible in water, ethanol, ether |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Fine Fragrance | 0.01-0.1% | Up to 0.5% | For animalic/milky effects |
| Flavorings | 5-50 ppm | Up to 100 ppm | Dairy flavor enhancement |
| Functional Fragrances | 0.001-0.01% | Up to 0.05% | Masking malodors |
Classic Accords
Tip: Always pre-dilute to 1% or lower before blending – direct use will contaminate equipment.
Alternatives & Comparisons
Less aggressive sibling with similar dairy character but reduced vomit nuance. Preferable for mainstream applications.
Longer carbon chain produces a more cheesy, less acidic odor profile for sustained dairy effects.
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. Consult current IFRA Standards Library before formulating.
IFRA Status
No IFRA restrictions. Classified as a weak sensitizer at high concentrations.
GHS Classification
RIFM Assessment
RIFM evaluation concludes safe use at current industry levels with proper handling precautions.
Sustainability
Most butyric acid is synthesized from petrochemical feedstocks, though some is produced via bacterial fermentation of plant biomass. The synthetic route has higher carbon footprint but avoids agricultural land use. Emerging bio-based production methods using genetically modified E. coli show promise for greener synthesis.
Explore Butyric acid
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References
- PubChem Compound Summary for Butyric Acid CID 264
Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Apr 2026.
Report a data errorIngredient Data Sheet
CAS 107-92-6Physical Properties
| Molecular Weight | 88.11 g/mol🔬 PubChem |
| LogP (Octanol-Water) | 0.8🔬 PubChem |
| Boiling Point | 163.5 °C🔬 EPA CompTox |
| Vapor Pressure | 0.43 mmHg @ 25°C📊 OPERA |
| Flash Point | 76.7 °C🔬 EPA CompTox |
| Involatility Index | 0.0494💻 Calculated |
| log Kp (skin permeability) | -2.669💻 Calculated |
| SMILES | CCCC(=O)O🔬 PubChem |
Volatility & Performance
| Fragrance Note | Top💻 Calculated |
| Volatility Class | Slow💻 Calculated |
| Persistence Score | 0.5 / 5💻 Calculated |
Odor & Flavor
| Primary Descriptors | buttery• leffingwell |
| “Powerful, penetrating, diffusive sour odor, reminiscent of rancid butter. However, being water-soluble, the odor "airs out" easier from a room than one should expect, also it can be washed off the skin easily with water, leaving little or no odor if washing is performed im-”📖 Arctander | |
| n-Butyric acid has a persistent, penetrating, rancid, butter-like odor and burning, acid taste.📖 Fenaroli | |
Flavor Notes (Arctander)
| “Used in flavor compositions, primarily in Butter flavor. Also in imitation Cheese, Nut, Fruit, in Butterscotch and Caramel, Rum, etc.”📖 Arctander |
Sensory Thresholds
| Odor Detection Threshold | 1.7412 ppm (n=24)📖 van Gemert |
Regulatory Status
| FEMA Number | FEMA 2221⚖️ 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: DTXSID8021515
Physical Properties
| Molecular Weight | 88.106 g/mol🔬 EPA CompTox |
| Density | 0.958 g/cm^3🔬 EPA CTX |
| Boiling Point | 163.7 °C🔬 EPA CTX |
| Melting Point | -6.708 °C🔬 EPA CTX |
| Flash Point | 72.192 °C🔬 EPA CTX |
| Refractive Index | 1.411 Dimensionless📊 OPERA |
| Molar Volume | 89.188 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | 1.598 Log10 unitless🔬 EPA CTX |
| LogD (pH 5.5) | 0.06 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | -1.744 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 4.23 Log10 unitless📊 OPERA |
| Water Solubility | 0.663 mol/L🔬 EPA CTX |
| Henry's Law Constant | 0 atm-m3/mole🔬 EPA CTX |
Transport Properties
| Vapor Pressure | 1.175 mmHg🔬 EPA CTX |
| Viscosity | 1.82 cP📊 OPERA |
| Surface Tension | 29.578 dyn/cm📊 OPERA |
| Thermal Conductivity | 147.456 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 | 22.145 cm^3/mol📊 OPERA |
| Polarizability | 8.779 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.
