Isoeugenol (trans) (CAS 97-54-1) — Spicy Heart Note Fragrance Ingredient
Isoeugenol (trans)
CAS 97-54-1
What Is Isoeugenol (trans)?
Isoeugenol is a warm, clove-like aromatic found in perfumes, soaps, and candles. It’s the synthetic version of a compound naturally present in ylang-ylang and nutmeg. This ingredient adds a spicy depth to fragrances, often blending with florals to create rich oriental accords. Its ability to evoke both natural warmth and sophisticated spice makes it a perfumer’s favorite for adding complexity.
Safety Profile
USE WITH AWARENESSWhat Does Isoeugenol (trans) Smell Like?
Isoeugenol unfolds with an intense clove-like punch – warm, slightly medicinal, and deeply aromatic. The initial sharpness mellows into a velvety sweet-spice character reminiscent of carnations and aged pipe tobacco. As a heart note, it demonstrates remarkable tenacity, gradually revealing woody-ambery facets that blend seamlessly with florals. The dry-down leaves a faint balsamic trail with hints of vanilla, making it particularly valuable in oriental compositions where it acts as both a bridge and fixative.
Scent Profile
In Famous Fragrances
Fragrance associations may not reflect actual formulations.
Isoeugenol provides the spicy clove backbone that defines this oriental legend, amplifying the exotic blend of florals and resins while adding warmth and diffusion.
Here isoeugenol’s sharp pepper facets are showcased, creating an illusion of freshly cracked peppercorns blended with carnation-like spice.
The modern version uses isoeugenol to reinforce the carnation accord, adding depth to the lavender-citrus opening and vanilla base.
Isoeugenol contributes to the chypre’s spicy heart, bridging between citrus top notes and oakmoss base with its balsamic warmth.
The bold spice in this oriental-balsamic owes much to isoeugenol’s tenacious clove character that persists through the fragrance’s development.
2D Molecular Structure
SMILES: COC1=CC(C=CC)=CC=C1O
Chemistry, Properties & Perfumer Guide
The Chemistry
Isoeugenol is a phenylpropene, specifically the trans-isomer of 4-hydroxy-3-methoxy-1-propenylbenzene. While naturally occurring in essential oils, commercial isoeugenol is typically synthesized from eugenol via isomerization. The trans configuration is more stable and exhibits superior odor characteristics compared to the cis form. Modern production often employs catalytic processes using ruthenium or rhodium complexes to achieve high yields of the desired isomer. Its phenolic hydroxyl group makes it moderately polar, while the propenyl side chain contributes to its volatility and diffusion characteristics.
Physical & Chemical Properties
| Boiling Point | 266 °C |
|---|---|
| Flash Point | >110 °C |
| Density | 1.08 g/cm³ |
| Refractive Index | 1.573-1.578 |
| Vapor Pressure | 0.001 mmHg at 25°C |
| Appearance | Colorless to pale yellow viscous liquid |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Fine Fragrance | 0.5-2% | Up to 5% | Spicy heart note in orientals |
| Soap | 0.1-0.5% | Up to 1% | Provides warm spice character |
| Candles | 0.2-1% | Up to 2% | Diffuses well in hot throw |
| Leave-on Cosmetics | 0.01-0.02% | Max 0.02% | IFRA restricted |
Classic Accords
Tip: Combine with vanillin to enhance sweetness or with woody notes like cedar to emphasize its balsamic facets.
Alternatives & Comparisons
The parent molecule with stronger clove character but less sweetness and diffusion. Prefer when a sharper spice note is needed.
Ether derivative with similar odor profile but lower allergen potential and better stability in alkaline products.
Hydrogenated version with reduced allergenicity while maintaining spice character, though less diffusive.
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
Restricted under IFRA Standard (Amendment 49): Maximum 0.02% in leave-on products, 0.2% in rinse-off. Prohibited in products intended to come into contact with mucous membranes.
EU Allergen Declaration
Listed in Annex III of EU Cosmetics Regulation – must be declared when concentration exceeds 0.001% in leave-on or 0.01% in rinse-off products.
GHS Classification
RIFM Assessment
RIFM assessment confirms skin sensitization potential at current use levels. Not considered phototoxic or mutagenic.
Sustainability
Synthetic production from renewable eugenol sources (clove leaf oil) offers consistent quality and reduces pressure on natural resources. Modern catalytic processes minimize waste and energy use. Being a high-impact material, even small quantities deliver significant olfactory effect, reducing environmental load per unit of fragrance performance.
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References
- IFRA Standards Library (2022). Restricted Ingredients List v49. IFRA Standard 49
- Bickers et al. (2005). A toxicologic and dermatologic assessment of phenylpropanoids. Food Chem Toxicol. PMID 16112377
- Surburg & Panten (2006). Common Fragrance and Flavor Materials. Wiley-VCH. ISBN 9783527608278
Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Mar 2026.
Report a data errorPhysicochemical Properties
DTXSID: DTXSID7022413
Physical Properties
| Molecular Weight | 164.204 g/mol🔬 EPA CompTox |
| Density | 1.081 g/cm^3🔬 EPA CTX |
| Boiling Point | 266.222 °C🔬 EPA CTX |
| Melting Point | -6.893 °C🔬 EPA CTX |
| Flash Point | 109.219 °C🔬 EPA CTX |
| Refractive Index | 1.578 Dimensionless📊 OPERA |
| Molar Volume | 152.841 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | 2.959 Log10 unitless🔬 EPA CTX |
| LogD (pH 5.5) | 2.796 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | 2.796 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 7.72 Log10 unitless📊 OPERA |
| Water Solubility | 0.005 mol/L🔬 EPA CTX |
| Henry's Law Constant | 0 atm-m3/mole🔬 EPA CTX |
Transport Properties
| Vapor Pressure | 0.014 mmHg🔬 EPA CTX |
| Viscosity | 4.746 cP📊 OPERA |
| Surface Tension | 37.829 dyn/cm📊 OPERA |
Molecular Descriptors
| Topological Polar Surface Area | 29.46 Ų💻 Computed |
| H-Bond Donors | 1 count💻 Computed |
| H-Bond Acceptors | 2 count💻 Computed |
| Rotatable Bonds | 2 count💻 Computed |
| Aromatic Rings | 1 count💻 Computed |
| Molar Refractivity | 50.702 cm^3/mol📊 OPERA |
| Polarizability | 20.1 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.
