Propylene Glycol (CAS 57-55-6) — Sweet Heart Note Fragrance Ingredient
Propylene Glycol
CAS 57-55-6
What Is Propylene Glycol?
Propylene glycol is a synthetic liquid commonly used in cosmetics, pharmaceuticals, and food products. You’ll find it in moisturizers, deodorants, and even some processed foods as a humectant and solvent. This versatile ingredient helps products retain moisture and improves texture. While it’s generally recognized as safe, some individuals with sensitive skin may experience irritation from high concentrations.
Safety Profile
GENERALLY SAFEWhat Does Propylene Glycol Smell Like?
Propylene glycol is practically odorless, presenting as a neutral carrier with minimal olfactory impact. Its slight sweetness is only detectable at very high concentrations, resembling a faint, clean alcohol note. In formulations, it serves as an invisible workhorse rather than a scent contributor, allowing other aromatic compounds to shine without interference. The complete lack of top, heart, or base characteristics makes it ideal for dilution and stabilization purposes.
Scent Profile
In Famous Fragrances
Fragrance associations may not reflect actual formulations.
Used as a solvent and carrier for the bright citrus and green tea notes, helping maintain the fragrance’s fresh, clean character without adding its own scent.
Propylene glycol helps stabilize the aquatic and citrus notes while preventing crystallization of other ingredients in this fresh marine fragrance.
Acts as a neutral base for the sparkling citrus and woody notes, ensuring consistent performance without altering the intended scent profile.
Used as a solvent for floral absolutes in this rich bouquet, helping maintain clarity and preventing oil separation in the complex formula.
Provides a neutral medium for the woody-ambery accord, ensuring even distribution of ingredients throughout the fragrance’s development.
2D Molecular Structure
SMILES: CC(O)CO
Chemistry, Properties & Perfumer Guide
The Chemistry
Propylene glycol (1,2-propanediol) is a small diol belonging to the alcohol chemical class. This synthetic compound is produced industrially by hydrolysis of propylene oxide, derived from petroleum refining. Unlike its relative ethylene glycol, it features a secondary hydroxyl group that contributes to its lower toxicity. The molecule’s amphiphilic nature (both hydrophilic and lipophilic properties) makes it an excellent solvent for a wide range of organic compounds. While it exists as a racemic mixture in commercial products, the (S)-(+)-enantiomer occurs naturally in some fermented foods.
Physical & Chemical Properties
| Boiling Point | 188.2 °C |
|---|---|
| Melting Point | -60 °C |
| Flash Point | 99 °C |
| Density | 1.036 g/cm³ |
| Refractive Index | 1.431-1.433 |
| Vapor Pressure | 0.08 mmHg at 20 °C |
| Solubility | Miscible with water |
| XLogP | -0.9 |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Fine Fragrance | 5-15% | 1-30% | Solvent and viscosity modifier |
| Cosmetics | 10-20% | 1-50% | Humectant and delivery system |
| Pharmaceuticals | 10-30% | 1-95% | Drug solvent and preservative |
| Food | 0.1-5% | 0.01-15% | Humectant and texturizer |
Classic Accords
Tip: Use to prevent crystallization of difficult materials like coumarin or vanillin in alcohol-based perfumes.
Alternatives & Comparisons
Higher molecular weight glycol with slower evaporation rate, useful for more viscous formulations requiring extended release.
Four-carbon glycol with similar solvent properties but slightly more emollient feel, often used in skincare fragrances.
Natural triol with superior humectant properties but higher viscosity and potential for microbial growth in formulations.
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. IFRA, REACH, EU Cosmetics Regulation standards update periodically. Consult current IFRA Standards Library before formulating. Not legal or regulatory advice.
IFRA Status
Not restricted by IFRA. Approved for use in all fragrance categories without limitations.
RIFM Assessment
RIFM evaluation confirms safety for current use levels in fragrances, with no significant irritation or sensitization potential at recommended concentrations.
Sustainability
While propylene glycol is petroleum-derived, its efficient production process and low environmental impact make it a practical choice. Some bio-based versions are now available from renewable resources like corn or sugarcane, offering reduced carbon footprint. The material is readily biodegradable (90% in 28 days) and has low aquatic toxicity, making it environmentally preferable to many alternative solvents.
Explore Propylene Glycol
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References
- PubChem Compound Summary for CID 1030, Propylene Glycol PubChem
- Fiume et al. (2012). Safety Assessment of Propylene Glycol, Tripropylene Glycol, and PPGs as Used in Cosmetics. PMID 22752825
- OECD SIDS Initial Assessment Report for Propylene Glycol OECD SIDS
Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Mar 2026.
Report a data errorIngredient Data Sheet
CAS 57-55-6Physical Properties
| Molecular Weight | 76.09 g/mol🔬 PubChem |
| LogP (Octanol-Water) | -0.9🔬 PubChem |
| Boiling Point | 188.2 °C🔬 EPA CompTox |
| Vapor Pressure | 0.08 mmHg @ 25°C📊 OPERA |
| Flash Point | 98.9 °C🔬 EPA CompTox |
| Involatility Index | 0.0099💻 Calculated |
| log Kp (skin permeability) | -3.803💻 Calculated |
| SMILES | CC(CO)O🔬 PubChem |
Volatility & Performance
| Fragrance Note | Top💻 Calculated |
| Volatility Class | Very slow💻 Calculated |
| Persistence Score | 0.8 / 5💻 Calculated |
Odor & Flavor
| Primary Descriptors | odorless• leffingwell |
| Functional Groups | alcohol💻 RDKit |
| “It finds very extensive use as a diluent or solvent in flavor compositions, mainly due to its low toxicity, absence of color and odor and to its mild, sweet taste. It is a fairly good solvent, although inferior to Ethyl alcohol in many respects, but it may replace alcohol in many products where alcohol tax can cause a problem.”📖 Arctander | |
| Propylene glycol has a slight, characteristic taste. It is practically odorless. It absorbs moisture when exposed to moist air.📖 Fenaroli | |
Flavor Notes (Arctander)
| “Miscible with water, Glycerin, alcohol and most of the common perfume and flavor oils, but not in Terpenes and many other hydrocarbons, poorly in aromatic Allyl- and Propenyl-derivatives, etc. Practically insoluble in vegetable oils and fats. Mild, sweet taste in aqueous solution, slightly burning o”📖 Arctander |
Sensory Thresholds
| Odor Detection Threshold | 73.7564 ppm (n=2)📖 van Gemert |
Regulatory Status
| 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: DTXSID0021206
Physical Properties
| Molecular Weight | 76.095 g/mol🔬 EPA CompTox |
| Density | 1.054 g/cm^3🔬 EPA CTX |
| Boiling Point | 187.356 °C🔬 EPA CTX |
| Melting Point | -59.889 °C🔬 EPA CTX |
| Flash Point | 100.827 °C🔬 EPA CTX |
| Refractive Index | 1.43 Dimensionless📊 OPERA |
| Molar Volume | 73.444 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | -0.761 Log10 unitless🔬 EPA CTX |
| LogD (pH 5.5) | -0.969 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | -0.969 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 6.74 Log10 unitless📊 OPERA |
| Water Solubility | 13.165 mol/L🔬 EPA CTX |
| Henry's Law Constant | 0 atm-m3/mole🔬 EPA CTX |
Transport Properties
| Vapor Pressure | 0.112 mmHg🔬 EPA CTX |
| Viscosity | 12.63 cP📊 OPERA |
| Surface Tension | 35.549 dyn/cm📊 OPERA |
| Thermal Conductivity | 184.634 mW/(m*K)📊 OPERA |
Molecular Descriptors
| Topological Polar Surface Area | 40.46 Ų💻 Computed |
| H-Bond Donors | 2 count💻 Computed |
| H-Bond Acceptors | 2 count💻 Computed |
| Rotatable Bonds | 1 count💻 Computed |
| Aromatic Rings | 0 count💻 Computed |
| Molar Refractivity | 18.976 cm^3/mol📊 OPERA |
| Polarizability | 7.523 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.
