Ionone Alpha (CAS 127-41-3) — Floral Base Note Fragrance Ingredient
Ionone Alpha
CAS 127-41-3
What Is Ionone Alpha?
Alpha-ionone is a violet-scented compound found naturally in violets and raspberries, often used to create floral and fruity perfume accords. It’s a key ingredient in many luxury fragrances and some flavored products. This molecule matters because it delivers a delicate floralcy that’s more refined than actual violet extracts, allowing perfumers to create sophisticated violet accords without the heavy, powdery aspects of natural materials.
Safety Profile
GENERALLY SAFE
What Does Ionone Alpha Smell Like?
Alpha-ionone opens with a crisp, dewy violet leaf impression – imagine crushed petals with a green stem freshness. Within minutes, it blossoms into the quintessential violet flower scent: powdery yet fresh, floral yet slightly fruity like raspberry jam. The dry-down reveals a soft woody-ambery base that lingers as a skin scent. Unlike beta-ionone’s heavier character, alpha-ionone maintains an airy quality throughout its evolution, like violet watercolor fading on paper.
Scent Profile
In Famous Fragrances
Fragrance associations may not reflect actual formulations.
Alpha-ionone creates the signature melancholy violet accord that floats above iris and vanilla, evoking raindrops on spring flowers.
Used in overdose to modernize the violet theme with a candied, almost fizzy quality that contrasts with woody amber base notes.
Alpha-ionone’s green facets are amplified with birch and incense to create a ‘smoky violet’ effect that defies floral conventions.
The molecule’s woody potential is exploited by pairing with sandalwood, creating a violet that grows from forest floor rather than garden bed.
Alpha-ionone provides the floral core that bridges between tart cassis top notes and earthy orris root in this urban violet interpretation.
2D Molecular Structure
SMILES: CC(=O)\C=C\C1C(C)=CCCC1(C)C
Chemistry, Properties & Perfumer Guide
The Chemistry
Alpha-ionone (C13H20O) is a cyclic terpenoid ketone belonging to the ionone family, characterized by a cyclohexenone ring with a methyl group at position 3 and a trimethylcyclohexenyl side chain. Naturally occurring in violets (Viola odorata) and raspberries, it’s typically synthesized via acid-catalyzed cyclization of pseudoionone derived from citral. The alpha isomer differs from beta-ionone in the position of the double bond in the cyclohexenone ring, which significantly impacts odor quality. Commercial alpha-ionone often contains some beta-isomer as a byproduct of synthesis.
Physical & Chemical Properties
| Boiling Point | 237 °C |
|---|---|
| Density | 0.93 g/cm³ |
| Refractive Index | 1.497-1.502 |
| Flash Point | >100 °C |
| Solubility | Insoluble in water, soluble in alcohol and oils |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Fine Fragrance | 1-3% | Up to 5% | Violet floralcy modifier |
| Soap | 0.5-1% | Up to 2% | Stable in alkaline conditions |
| Candles | 0.2-0.8% | Up to 1.5% | Good thermal stability |
| Flavors | 10-50 ppm | Up to 100 ppm | Raspberry/violet nuance |
Classic Accords
+ Cassis Base + Aldehydes = Sparkling Berry
+ Cedarwood + Vanilla = Woody Floral
Tip: Use alpha-ionone with ionone beta at 3:1 ratio for most natural violet effect.
Alternatives & Comparisons
More intense, woody-violet character with better tenacity but less freshness. Use when heavier violet impact is needed.
Softer, more powdery alternative with excellent blending properties for complex floral bases.
Natural option with green, cucumber-like facets but much lower concentration of ionones.
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
No IFRA restrictions (Amendment 49). Considered safe at all concentrations for all applications.
EU Allergen Declaration
Not listed in EU allergen regulation (EC) No 1223/2009 Annex III.
RIFM Assessment
RIFM safety assessment confirms safe use in current practices (2015). No evidence of phototoxicity or significant sensitization at typical use levels.
Sustainability
Most alpha-ionone is synthesized from petrochemical precursors, though some producers use bio-based citral from lemongrass oil. Synthesis routes have been optimized to minimize waste and energy use. Unlike natural violet extracts which require vast quantities of flowers (approximately 10,000 kg of violets per 1 kg of absolute), synthetic alpha-ionone provides consistent quality without agricultural land use.
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Industry & Science Data
References
- Bauer, K. et al. (2001). Common Fragrance and Flavor Materials. Wiley-VCH.
- Sell, C. (2006). The Chemistry of Fragrances. RSC Publishing.
- Brenna, E. et al. (2003). Ionones: Synthesis and Odor Activity. Chemistry & Biodiversity. DOI:10.1002/cbdv.200390001
Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Mar 2026.
Ingredient Data Sheet
CAS 127-41-3Physical Properties
| Molecular Weight | 192.3 g/mol🔬 PubChem |
| LogP (Octanol-Water) | 3🔬 PubChem |
| Boiling Point | 258 °C🔬 EPA CompTox |
| Vapor Pressure | 0.019 mmHg @ 25°C📊 OPERA |
| Flash Point | 47.8 °C🔬 EPA CompTox |
| Involatility Index | 0.0015💻 Calculated |
| log Kp (skin permeability) | -1.743💻 Calculated |
| SMILES | CC1=CCCC(C1C=CC(=O)C)(C)C🔬 PubChem |
Volatility & Performance
| Fragrance Note | Heart💻 Calculated |
| Volatility Class | Very slow💻 Calculated |
| Persistence Score | 3.2 / 5💻 Calculated |
Odor & Flavor
| Primary Descriptors | balsamicvioletwoody• leffingwell |
| Functional Groups | ketonealkene💻 RDKit |
| “odor with some resemblance to the odor of bera-Ionone. for such odor types is extremely small and 2t Perfume very few perfume laboratories seem to carry CyclocitraI via Grig-nard synthesis with Cyan- this material. I I 1- The odor varies according to isomer ratio, Hzd ‘ CH3 but can generally be classified as warm, Violet- \c{c\cH like, sweet, yet somewhat powdery and very 3 tenacious.”📖 Arctander | |
| a-Ionone has a warm, woody, berry characteristic violet-like odor. The composition of commercial ionones varies widely in the proportion of a- and b-isomers; the specifications given below refer to the best grade of a- and b-ionones and to a commercial grade that contains both a- and b-ionones.📖 Fenaroli | |
Sensory Thresholds
| Odor Detection Threshold | 0.0014 ppm (n=14)📖 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: DTXSID0035160
Physical Properties
| Molecular Weight | 192.302 g/mol🔬 EPA CompTox |
| Density | 0.925 g/cm^3🔬 EPA CTX |
| Boiling Point | 248.62 °C🔬 EPA CTX |
| Melting Point | 24.638 °C📊 OPERA |
| Flash Point | 103.2 °C🔬 EPA CTX |
| Refractive Index | 1.512 Dimensionless📊 OPERA |
| Molar Volume | 205.659 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | 3.855 Log10 unitless🔬 EPA CTX |
| LogD (pH 5.5) | 3.855 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | 3.855 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 6.12 Log10 unitless📊 OPERA |
| Water Solubility | 0.953 mol/L🔬 EPA CTX |
| Henry's Law Constant | 0 atm-m3/mole📊 OPERA |
Transport Properties
| Vapor Pressure | 0.017 mmHg🔬 EPA CTX |
| Surface Tension | 32.095 dyn/cm📊 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 | 2 count💻 Computed |
| Aromatic Rings | 0 count💻 Computed |
| Molar Refractivity | 61.708 cm^3/mol📊 OPERA |
| Polarizability | 24.463 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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