4-Methyl-5-thiazoleethanol (CAS 137-00-8) — Spicy Heart to base Note Fragrance Ingredient
4-Methyl-5-thiazoleethanol
CAS 137-00-8
What Is 4-Methyl-5-thiazoleethanol?
4-Methyl-5-thiazoleethanol is a synthetic aroma chemical that adds a meaty, roasted character to savory flavors and fragrances. You might encounter it in beef bouillon, processed meats, or savory snack seasonings. This ingredient matters because it creates umami depth and meaty authenticity in both food and fragrance applications, bridging the gap between culinary and perfumery arts.
Safety Profile
USE WITH AWARENESSWhat Does 4-Methyl-5-thiazoleethanol Smell Like?
Pungent and savory at first encounter, like a sizzling steak crust or roasted coffee beans, with an underlying sulfurous complexity reminiscent of fried onions. The top note has a sharp, almost metallic meatiness that gradually mellows into a warm, brothy heart. The dry-down reveals a lingering nutty character with subtle earthy undertones, like mushroom stock reduced to its essence. In dilution, it becomes more refined – think prime rib au jus rather than raw meat.
In Famous Fragrances
Fragrance associations may not reflect actual formulations.
Used minimally to amplify the controversial blood-like metallic aspects, creating unsettling realism in this avant-garde composition.
Provides subtle animalic depth to the leather accord, suggesting well-worn saddles and the warmth of human contact.
2D Molecular Structure
SMILES: CC1=C(CCO)SC=N1
Chemistry, Properties & Perfumer Guide
The Chemistry
A thiazole derivative with both heterocyclic and alcohol functional groups. The thiazole ring contributes sulfurous, roasted notes while the ethanol side chain modulates volatility. Typically synthesized through condensation reactions of α-mercaptoketones with α-halo carbonyl compounds. The methyl group at the 4-position sterically influences odor character, making it more meaty than simpler thiazoles.
Physical & Chemical Properties
| Appearance | Colorless to pale yellow liquid |
|---|---|
| Boiling Point | ~220 °C (estimated) |
| Density | ~1.15 g/cm³ (estimated) |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Fine Fragrance | 0.01-0.1% | Up to 0.5% | Used for animalic accents |
| Functional Fragrance | 0.001-0.01% | Up to 0.05% | Masking agent for rubber/plastic |
Classic Accords
Tip: Always pre-dilute to 1% or lower before incorporation due to intense odor impact.
Alternatives & Comparisons
Provides similar meaty character but with more popcorn-like top notes and less sulfurous depth.
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. Consult current IFRA Standards Library before formulating.
IFRA Status
Not currently restricted by IFRA. Self-regulated by industry due to potency.
GHS Classification
RIFM Assessment
RIFM evaluation ongoing. Preliminary data suggests safe use at current levels.
Sustainability
Synthesized from petrochemical precursors with relatively low environmental impact due to small usage quantities. No known natural sources, making synthetic production essential for this aroma chemical.
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References
- Burdock, G.A. (2010). Fenaroli’s Handbook of Flavor Ingredients. CRC Press. ISBN 9781420090772
Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Apr 2026.
Report a data errorIngredient Data Sheet
CAS 137-00-8Physical Properties
| Molecular Weight | 143.21 g/mol🔬 PubChem |
| LogP (Octanol-Water) | 0.8🔬 PubChem |
| Boiling Point | 135 °C🔬 EPA CompTox |
| log Kp (skin permeability) | -3.006💻 Calculated |
| SMILES | CC1=C(SC=N1)CCO🔬 PubChem |
Volatility & Performance
| Fragrance Note | Top💻 Calculated |
Odor & Flavor
| Primary Descriptors | nutty• leffingwell |
| Functional Groups | alcoholaromatic💻 RDKit |
| “Sweet, animal-herbaceous and very tenacious odor.”📖 Arctander | |
| 4-Methyl-5-thiazoleethanol has a disagreeable odor typical of thiazole compounds; somewhat pleasant, reminiscent of beef and nut-like, on extreme dilution.📖 Fenaroli | |
Sensory Thresholds
| Odor Detection Threshold | 3.3912 ppm (n=2)📖 van Gemert |
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: DTXSID3044382
Physical Properties
| Molecular Weight | 143.2 g/mol🔬 EPA CompTox |
| Density | 1.173 g/cm^3📊 OPERA |
| Boiling Point | 250.188 °C📊 OPERA |
| Melting Point | 28.228 °C📊 OPERA |
| Flash Point | 92.472 °C📊 OPERA |
| Refractive Index | 1.564 Dimensionless📊 OPERA |
| Molar Volume | 118.735 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | 0.844 Log10 unitless📊 OPERA |
| LogD (pH 5.5) | 0.838 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | 0.844 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 7.2 Log10 unitless📊 OPERA |
| Water Solubility | 0.085 mol/L📊 OPERA |
| Henry's Law Constant | 0 atm-m3/mole📊 OPERA |
Transport Properties
| Vapor Pressure | 0.038 mmHg📊 OPERA |
| Viscosity | 13.597 cP📊 OPERA |
| Surface Tension | 43.496 dyn/cm📊 OPERA |
Molecular Descriptors
| Topological Polar Surface Area | 33.12 Ų💻 Computed |
| H-Bond Donors | 1 count💻 Computed |
| H-Bond Acceptors | 3 count💻 Computed |
| Rotatable Bonds | 2 count💻 Computed |
| Aromatic Rings | 1 count💻 Computed |
| Molar Refractivity | 38.638 cm^3/mol📊 OPERA |
| Polarizability | 15.317 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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