Propionic acid (CAS 79-09-4) — Citrus Top Note Fragrance Ingredient
Propionic acid
CAS 79-09-4
What Is Propionic acid?
Propionic acid is a synthetic organic compound primarily encountered as a food preservative (E280) in baked goods and animal feed. Its sharp, pungent odor is noticeable in very low concentrations. While not commonly used in fine fragrances, it appears in some industrial and novelty scents for its distinctive sour, cheesy character.
Safety Profile
USE WITH AWARENESSWhat Does Propionic acid Smell Like?
Propionic acid delivers an intensely sharp, acrid punch reminiscent of vinegar’s aggressive cousin. The opening is a nose-wrinkling assault of sour dairy and sweaty cheese, with a disturbing fermented undertone. As it dries, the acidity softens slightly into a persistent rancid butter effect, making this more useful for creating challenging accords than for direct perfumery applications. The dry-down leaves a faint metallic tang that clings stubbornly to surfaces.
2D Molecular Structure
SMILES: CCC(O)=O
Chemistry, Properties & Perfumer Guide
The Chemistry
Propionic acid (CH3CH2COOH) is a simple carboxylic acid, the third member of the saturated fatty acid series. Industrially produced via hydrocarboxylation of ethylene using nickel carbonyl or propionaldehyde oxidation, it’s rarely found in nature except as a metabolic byproduct. The molecule lacks chirality but forms hydrogen-bonded dimers that influence its volatility and persistence. Its low molecular weight (74.08 g/mol) contributes to high volatility and sharp odor profile.
Physical & Chemical Properties
| Boiling Point | 141 °C |
|---|---|
| Melting Point | -21 °C |
| Density | 0.993 g/cm³ |
| Vapor Pressure | 3.53 mmHg at 25°C |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Industrial Scents | 0.01-0.1% | Up to 0.5% | For harsh, challenging effects |
| Novelty Fragrances | trace | 0.001-0.01% | Used sparingly for shock value |
Classic Accords
Tip: Always pre-dilute to 1% or lower before adding to blends due to extreme potency and corrosiveness.
Alternatives & Comparisons
Offers similar sour dairy notes but with more body and slightly less sharpness, better for fermented cheese accords.
Provides comparable acidity with added sweaty, foot-like nuances for extreme animalic effects.
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. Consult current IFRA Standards Library before formulating.
IFRA Status
Not formally restricted by IFRA but generally avoided in consumer fragrances due to harshness.
GHS Classification
RIFM Assessment
Not evaluated by RIFM for fragrance use due to limited cosmetic applications.
Sustainability
Produced from petrochemical feedstocks via energy-intensive processes. No significant natural sources exist for commercial extraction. Waste streams require neutralization due to corrosiveness, but biodegradation occurs rapidly in the environment.
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References
- PubChem Compound Summary for Propionic acid CID 1032
- EFSA Panel on Food Additives (2014). Re-evaluation of propionic acid (E 280). EFSA Journal. DOI:10.2903/j.efsa.2014.3779
Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Apr 2026.
Report a data errorIngredient Data Sheet
CAS 79-09-4Physical Properties
| Molecular Weight | 74.08 g/mol🔬 PubChem |
| LogP (Octanol-Water) | 0.3🔬 PubChem |
| Boiling Point | 140.7 °C🔬 EPA CompTox |
| Vapor Pressure | 2.9 mmHg @ 25°C📊 OPERA |
| Flash Point | 54.4 °C🔬 EPA CompTox |
| Involatility Index | 0.3631💻 Calculated |
| log Kp (skin permeability) | -2.939💻 Calculated |
| SMILES | CCC(=O)O🔬 PubChem |
Volatility & Performance
| Fragrance Note | Top💻 Calculated |
| Volatility Class | Moderate💻 Calculated |
| Persistence Score | 0.5 / 5💻 Calculated |
Odor & Flavor
| Primary Descriptors | milkypungent• leffingwell |
| “Pungent sour odor reminiscent of sour Milk, Cheese or sour Butter.”📖 Arctander | |
| Propionic acid has a pungent, rancid odor. Propionic acid is an aliphatic monocarboxylic acid. For a detailed description of this compound refer to Burdock (1997).📖 Fenaroli | |
Flavor Notes (Arctander)
| “Sour taste in aqueous solution, pleasant- sour, more unpleasant taste. in many flavor compositions. As a fungicide”📖 Arctander |
Sensory Thresholds
| Odor Detection Threshold | 2.5938 ppm (n=27)📖 van Gemert |
Regulatory Status
| FEMA Number | FEMA 2924⚖️ 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: DTXSID8025961
Physical Properties
| Molecular Weight | 74.079 g/mol🔬 EPA CompTox |
| Density | 0.991 g/cm^3🔬 EPA CTX |
| Boiling Point | 140.971 °C🔬 EPA CTX |
| Melting Point | -20.893 °C🔬 EPA CTX |
| Flash Point | 52.969 °C🔬 EPA CTX |
| Refractive Index | 1.397 Dimensionless📊 OPERA |
| Molar Volume | 72.682 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | 0.33 Log10 unitless🔬 EPA CTX |
| LogD (pH 5.5) | -0.432 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | -2.244 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 3.95 Log10 unitless📊 OPERA |
| Water Solubility | 13.498 mol/L🔬 EPA CTX |
| Henry's Law Constant | 0 atm-m3/mole🔬 EPA CTX |
Transport Properties
| Vapor Pressure | 3.273 mmHg🔬 EPA CTX |
| Viscosity | 1.406 cP📊 OPERA |
| Surface Tension | 29.443 dyn/cm📊 OPERA |
| Thermal Conductivity | 151.112 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 | 1 count💻 Computed |
| Aromatic Rings | 0 count💻 Computed |
| Molar Refractivity | 17.512 cm^3/mol📊 OPERA |
| Polarizability | 6.942 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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