2-Isobutylthiazole (CAS 18640-74-9) — Green Top to middle Note Fragrance Ingredient
2-Isobutylthiazole
CAS 18640-74-9
What Is 2-Isobutylthiazole?
2-Isobutylthiazole is a synthetic compound used to create fresh, green, and tomato-like aromas in perfumes and flavorings. You’ll encounter it in fragrances that aim for a crisp, vegetal character. This ingredient matters because it provides a hyper-realistic ‘just picked’ green note that’s hard to achieve with natural materials alone, making it invaluable for modern fresh fragrances and fruity accords.
Safety Profile
USE WITH AWARENESSWhat Does 2-Isobutylthiazole Smell Like?
2-Isobutylthiazole bursts with an intensely green, almost aggressive vegetal aroma reminiscent of freshly crushed tomato leaves and cut bell peppers. The initial pungency mellows into a more refined greenness, like dewy grass at dawn, with subtle earthy undertones. In dry-down, it leaves a whisper of herbal freshness that blends beautifully with citrus and floral notes. Though powerful at first, it behaves surprisingly well in dilution, revealing a sophisticated green character that can make floral compositions smell more alive and natural.
In Famous Fragrances
Fragrance associations may not reflect actual formulations.
Used for its hyper-realistic tomato leaf effect, creating the illusion of sun-warmed vegetation in this groundbreaking green floral.
Provides the wet, crushed greenery note that makes this monsoon-inspired fragrance so vividly atmospheric.
Accentuates the oakmoss with an extra layer of dewy greenness, enhancing the forest floor illusion.
2D Molecular Structure
SMILES: CC(C)CC1=NC=CS1
Chemistry, Properties & Perfumer Guide
The Chemistry
2-Isobutylthiazole belongs to the thiazole class of heterocyclic compounds, characterized by a five-membered ring containing both sulfur and nitrogen atoms. While thiazoles occur naturally in some foods (like tomatoes), perfumery uses synthetically produced material for consistency. It’s typically synthesized via Hantzsch thiazole synthesis, reacting α-halo ketones with thioamides. The isobutyl side chain contributes to both its volatility and distinctive green odor profile. Unlike some thiazoles that have meaty aromas, the branched alkyl group here directs the scent toward fresh vegetation.
Physical & Chemical Properties
| Appearance | Colorless to pale yellow liquid |
|---|---|
| Boiling Point | ~60-62 °C at 0.5 mmHg |
| Density | ~0.99 g/cm³ |
| Refractive Index | ~1.495 |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Fine Fragrance | 0.01-0.1% | Up to 0.3% | Powerful effect even at low concentrations |
| Functional Fragrance | 0.001-0.01% | Up to 0.05% | Adds freshness to detergents |
Classic Accords
Tip: Always pre-dilute to 1% or lower before blending to avoid overwhelming other notes.
Alternatives & Comparisons
For a softer, grassier green note without the tomato leaf intensity.
When you need similar greenness but with better floral compatibility.
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. Consult current IFRA Standards Library before formulating.
IFRA Status
No IFRA restrictions currently apply to 2-Isobutylthiazole (as of 54th Amendment).
GHS Classification
RIFM Assessment
RIFM assessment confirms safe use at current industry levels with no sensitization concerns.
Sustainability
As a synthetic material, 2-Isobutylthiazole avoids agricultural impacts but requires energy-intensive production. Its potency means minimal quantities are needed, reducing overall environmental load compared to some natural green materials like galbanum resin which requires wild harvesting.
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References
- Burdock, G.A. (2010). Fenaroli’s Handbook of Flavor Ingredients. CRC Press. ISBN 9781420090869
Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Apr 2026.
Report a data errorIngredient Data Sheet
CAS 18640-74-9Physical Properties
| Molecular Weight | 141.24 g/mol🔬 PubChem |
| LogP (Octanol-Water) | 2.6🔬 PubChem |
| Boiling Point | 191 °C🔬 EPA CompTox |
| Vapor Pressure | 0.871 mmHg @ 25°C📊 OPERA |
| Flash Point | 57.8 °C🔬 EPA CompTox |
| Involatility Index | 0.079💻 Calculated |
| log Kp (skin permeability) | -1.716💻 Calculated |
| SMILES | CC(C)CC1=NC=CS1🔬 PubChem |
Volatility & Performance
| Fragrance Note | Top💻 Calculated |
| Volatility Class | Slow💻 Calculated |
| Persistence Score | 0.5 / 5💻 Calculated |
Odor & Flavor
| Primary Descriptors | greenleafy• leffingwell |
| Functional Groups | aromatic💻 RDKit |
| 2-Isobutyl thiazole has a tomato leaf odor.📖 Fenaroli | |
Sensory Thresholds
| Odor Detection Threshold | 0.6084 ppm (n=6)📖 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: DTXSID5025653
Physical Properties
| Molecular Weight | 141.23 g/mol🔬 EPA CompTox |
| Density | 0.995 g/cm^3🔬 EPA CTX |
| Boiling Point | 184.891 °C📊 OPERA |
| Melting Point | -10.955 °C📊 OPERA |
| Flash Point | 54.184 °C📊 OPERA |
| Refractive Index | 1.512 Dimensionless📊 OPERA |
| Molar Volume | 138.344 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | 2.419 Log10 unitless📊 OPERA |
| LogD (pH 5.5) | 2.243 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | 2.414 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 4.32 Log10 unitless📊 OPERA |
| Water Solubility | 0.034 mol/L📊 OPERA |
| Henry's Law Constant | 0 atm-m3/mole📊 OPERA |
Transport Properties
| Vapor Pressure | 1.437 mmHg📊 OPERA |
| Viscosity | 2.701 cP📊 OPERA |
| Surface Tension | 33.045 dyn/cm📊 OPERA |
Molecular Descriptors
| Topological Polar Surface Area | 12.89 Ų💻 Computed |
| H-Bond Donors | 0 count💻 Computed |
| H-Bond Acceptors | 2 count💻 Computed |
| Rotatable Bonds | 2 count💻 Computed |
| Aromatic Rings | 1 count💻 Computed |
| Molar Refractivity | 41.502 cm^3/mol📊 OPERA |
| Polarizability | 16.453 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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