6-Isopropylquinoline (CAS 135-79-5) — Woody Middle Note Fragrance Ingredient
6-Isopropylquinoline
CAS 135-79-5
What Is 6-Isopropylquinoline?
6-Isopropylquinoline is a synthetic aroma chemical used in niche perfumery. It adds a distinctive leathery, woody character to fragrances. You’ll encounter it in avant-garde compositions that push olfactory boundaries. This molecule matters because it provides perfumers with a unique alternative to traditional leather notes, offering more complexity than simpler synthetic leather aromas.
Safety Profile
USE WITH AWARENESSWhat Does 6-Isopropylquinoline Smell Like?
6-Isopropylquinoline presents an intriguing duality – opening with sharp, almost medicinal quinolinic bitterness that quickly transforms into a rich leather foundation. Imagine aged book bindings meeting freshly tanned hides, with subtle tobacco undertones emerging during dry-down. The isopropyl group lends a slightly woody, camphoraceous edge that prevents the leather character from becoming overly animalic. In dilution, it reveals surprising floral facets reminiscent of chrysanthemum petals.
In Famous Fragrances
Fragrance associations may not reflect actual formulations.
Used to enhance the birch tar leather accord, providing intellectual bitterness that balances the formula’s floral heart.
Contributes to the hyper-realistic leather effect, adding structural complexity to the raspberry-leather juxtaposition.
2D Molecular Structure
SMILES: CC(C)C1=CC2=CC=CN=C2C=C1
Chemistry, Properties & Perfumer Guide
The Chemistry
6-Isopropylquinoline belongs to the quinoline class of heterocyclic aromatic compounds. The molecule features a nitrogen-containing bicyclic structure with an isopropyl group at the 6-position. Industrially synthesized through Skraup or Doebner-Miller reactions, this compound demonstrates how small alkyl substitutions dramatically alter odor profiles compared to unsubstituted quinoline. The isopropyl group increases volatility slightly while introducing new conformational possibilities that affect receptor binding.
Physical & Chemical Properties
| Appearance | Colorless to pale yellow liquid |
|---|---|
| Boiling Point | ~250 °C (estimated) |
| Density | ~1.05 g/cm³ (estimated) |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Fine Fragrance | 0.1-0.5% | Up to 1% | Powerful leather modifier |
| Functional Fragrance | 0.01-0.1% | Up to 0.2% | Used sparingly in leather cleaners |
Classic Accords
Tip: Use trace amounts (0.05-0.2%) to add intellectual depth to leather bases without overwhelming floral components.
Alternatives & Comparisons
The parent compound without isopropyl substitution, offering sharper, more medicinal leather notes but lacking the woody complexity.
Provides similar leather effects with slightly fruitier, less camphoraceous character due to different alkyl substitution.
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. Consult current IFRA Standards Library before formulating.
IFRA Status
Not currently restricted under IFRA standards. Listed as safe at current usage levels in fragrance applications.
GHS Classification
RIFM Assessment
RIFM has evaluated 6-isopropylquinoline and found it safe for use in fragrance at current industry levels.
Sustainability
As a synthetic material, 6-isopropylquinoline avoids natural resource depletion concerns. Production typically uses petrochemical feedstocks, though green chemistry approaches are being explored. The molecule’s potency means very small quantities are needed, reducing overall environmental impact per kilogram of finished product.
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References
- Bauer et al. (2001). Quinoline Derivatives in Perfumery. Flavour and Fragrance Journal.
Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Apr 2026.
Report a data errorIngredient Data Sheet
CAS 135-79-5Physical Properties
| Molecular Weight | 171.24 g/mol🔬 PubChem |
| LogP (Octanol-Water) | 3.3🔬 PubChem |
| Boiling Point | 267 °C🔬 EPA CompTox |
| Vapor Pressure | 0.01 mmHg @ 25°C📊 OPERA |
| Flash Point | 109.9 °C🔬 EPA CompTox |
| Involatility Index | 0.0008💻 Calculated |
| log Kp (skin permeability) | -1.402💻 Calculated |
| SMILES | CC(C)C1=CC2=C(C=C1)N=CC=C2🔬 PubChem |
Volatility & Performance
| Fragrance Note | Heart💻 Calculated |
| Volatility Class | Very slow💻 Calculated |
| Persistence Score | 3.7 / 5💻 Calculated |
Odor & Flavor
| Functional Groups | aromatic💻 RDKit |
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: DTXSID9047465
Physical Properties
| Molecular Weight | 171.243 g/mol🔬 EPA CompTox |
| Density | 1.057 g/cm^3📊 OPERA |
| Boiling Point | 275.577 °C📊 OPERA |
| Melting Point | 53.829 °C📊 OPERA |
| Flash Point | 116.668 °C📊 OPERA |
| Refractive Index | 1.591 Dimensionless📊 OPERA |
| Molar Volume | 166.845 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | 3.282 Log10 unitless📊 OPERA |
| LogD (pH 5.5) | 3.052 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | 3.276 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 6.67 Log10 unitless📊 OPERA |
| Water Solubility | 0.004 mol/L📊 OPERA |
| Henry's Law Constant | 0 atm-m3/mole📊 OPERA |
Transport Properties
| Vapor Pressure | 0.01 mmHg🔬 EPA CTX |
| Viscosity | 8.428 cP📊 OPERA |
| Surface Tension | 39.107 dyn/cm📊 OPERA |
| Thermal Conductivity | 132.086 mW/(m*K)📊 OPERA |
Molecular Descriptors
| Topological Polar Surface Area | 12.89 Ų💻 Computed |
| H-Bond Donors | 0 count💻 Computed |
| H-Bond Acceptors | 1 count💻 Computed |
| Rotatable Bonds | 1 count💻 Computed |
| Aromatic Rings | 2 count💻 Computed |
| Molar Refractivity | 56.372 cm^3/mol📊 OPERA |
| Polarizability | 22.347 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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