Dihydro-alpha-ionone (CAS 31499-72-6) — Woody Heart to base Note Fragrance Ingredient
Dihydro-alpha-ionone
CAS 31499-72-6
What Is Dihydro-alpha-ionone?
Dihydro-alpha-ionone is a synthetic fragrance ingredient that creates warm, woody floral notes. You’ll find it in perfumes, soaps, and candles where it adds depth without being overpowering. This molecule matters because it mimics expensive natural compounds at a fraction of the cost, allowing more affordable luxury fragrances. Its stability makes it ideal for products needing long-lasting scent.
Safety Profile
GENERALLY SAFEWhat Does Dihydro-alpha-ionone Smell Like?
Dihydro-alpha-ionone unfolds like sun-warmed cedarwood dipped in honeyed violets. The initial burst carries a crisp, almost citrus-tinged woodiness that quickly softens into velvety floral heart notes. Unlike its alpha-ionone parent, it lacks the sharp edges, delivering a rounded, powdery dry-down reminiscent of antique rose petals pressed between sandalwood book covers. The scent lingers close to skin with remarkable tenacity, evolving into a whisper of musky sweetness that harmonizes beautifully with amber bases.
In Famous Fragrances
Fragrance associations may not reflect actual formulations.
Provides the signature iris-violet accord with enhanced woody depth, balancing the fragrance’s powdery elegance with masculine structure.
Used as a cost-effective alternative to orris root, contributing to the timeless floral bouquet with its smooth woody-floral character.
2D Molecular Structure
SMILES: CC(=O)CCC1C(C)=CCCC1(C)C
Chemistry, Properties & Perfumer Guide
The Chemistry
Dihydro-alpha-ionone belongs to the ionone class of cyclic terpenoids, specifically a hydrogenated derivative of alpha-ionone. While ionones occur naturally in violets and orris root, this variant is exclusively synthetic. Industrial production typically involves hydrogenation of alpha-ionone over nickel catalysts, selectively saturating the conjugated double bond system. The resulting molecule exhibits greater stability than its parent compound while retaining the characteristic woody-floral odor profile. Chirality plays minimal role in its olfactory properties due to the symmetric reduction of the cyclic ketone.
Physical & Chemical Properties
| Appearance | Colorless to pale yellow liquid |
|---|---|
| Boiling Point | Approx. 250°C (estimated) |
| Density | ~0.92 g/cm³ (estimated) |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Fine Fragrance | 1-3% | Up to 5% | Woody-floral modifier |
| Soap | 0.5-1% | Up to 2% | Stable in alkaline systems |
Classic Accords
Tip: Use to bridge citrus top notes with woody bases while avoiding sharp ionone metallic tones.
Alternatives & Comparisons
When more pronounced violet-orris character is desired, though less stable in formulations.
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. Consult current IFRA Standards Library before formulating.
IFRA Status
Not restricted under current IFRA standards (Amendment 49).
RIFM Assessment
Considered safe for current use levels based on RIFM’s 2015 cyclic ketones assessment.
Sustainability
As a purely synthetic material, dihydro-alpha-ionone avoids pressure on natural violet and orris root supplies. Production requires petrochemical feedstocks but benefits from efficient catalytic processes with minimal waste. Its longevity in formulations reduces reapplications, indirectly lowering environmental impact.
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References
- Bauer et al. (2001). Common Fragrance and Flavor Materials. Wiley-VCH.
Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Apr 2026.
Report a data errorIngredient Data Sheet
CAS 31499-72-6Physical Properties
| Molecular Weight | 194.31 g/mol🔬 PubChem |
| LogP (Octanol-Water) | 2.8🔬 PubChem |
| Boiling Point | 277 °C🔬 EPA CompTox |
| Vapor Pressure | 0.0501 mmHg @ 25°C📊 OPERA |
| Flash Point | 98 °C🔬 EPA CompTox |
| Involatility Index | 0.0039💻 Calculated |
| log Kp (skin permeability) | -1.897💻 Calculated |
| SMILES | CC1=CCCC(C1CCC(=O)C)(C)C🔬 PubChem |
Volatility & Performance
| Fragrance Note | Heart💻 Calculated |
| Volatility Class | Very slow💻 Calculated |
| Persistence Score | 2.4 / 5💻 Calculated |
Odor & Flavor
| Primary Descriptors | floralfruityorrisvioletwoody• leffingwell |
| Functional Groups | ketonealkene💻 RDKit |
| “Rather "thin" oily-woody odor, somewhat "gassy" and weaker than alpha-Ionone with respect to Violet-note.”📖 Arctander | |
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: DTXSID40865599
Physical Properties
| Molecular Weight | 194.318 g/mol🔬 EPA CompTox |
| Density | 0.884 g/cm^3📊 OPERA |
| Boiling Point | 277 °C🔬 EPA CTX |
| Melting Point | 22.479 °C📊 OPERA |
| Flash Point | 98 °C🔬 EPA CTX |
| Refractive Index | 1.448 Dimensionless📊 OPERA |
| Molar Volume | 223.851 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | 4.115 Log10 unitless📊 OPERA |
| LogD (pH 5.5) | 4.115 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | 4.115 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 6.32 Log10 unitless📊 OPERA |
| Water Solubility | 0.001 mol/L📊 OPERA |
| Henry's Law Constant | 0 atm-m3/mole📊 OPERA |
Transport Properties
| Vapor Pressure | 0.026 mmHg📊 OPERA |
| Viscosity | 3.863 cP📊 OPERA |
| Surface Tension | 27.937 dyn/cm📊 OPERA |
| Thermal Conductivity | 128.555 mW/(m*K)📊 OPERA |
Molecular Descriptors
| Topological Polar Surface Area | 17.07 Ų💻 Computed |
| H-Bond Donors | 0 count💻 Computed |
| H-Bond Acceptors | 1 count💻 Computed |
| Rotatable Bonds | 3 count💻 Computed |
| Aromatic Rings | 0 count💻 Computed |
| Molar Refractivity | 59.922 cm^3/mol📊 OPERA |
| Polarizability | 23.755 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.
