Methyl Ionone Gamma A

Methyl Ionone Gamma A Technical Ingredient Overview

• 🏭 Manufacturer — IFF (International Flavors & Fragrances); also produced by major fragrance houses including Givaudan, Firmenich, Symrise

• 🔎 Chemical Name — Methyl ionone (mixture of isomers, predominantly α-isomethyl ionone)

• 🧪 Synonyms — Methylionone; Isoraldeine; Iralia; Methyl irisone; Ionone, methyl-; α-Isomethyl ionone (major component); Iraldeine gamma; Isoraldeine 95

• 📂 CAS Number — 1335-46-2 (mixture); Individual isomers: 127-42-4 (α-methylionone), 127-43-5 (β-methylionone), 127-51-5 (α-isomethyl ionone), 7779-30-8, 79-89-0, 1335-94-0

• 📘 FEMA Number — 2711 (methyl ionone mixture); 2714 (individual isomers)

• ⚖️ Molecular Weight — 206.33 g/mol (C₁₄H₂₂O)

• 📝 Odor Type — Floral-woody, violet

• 📈 Odor Strength — Medium to strong (varies by isomeric composition)

• 👃🏼 Odor Profile — Floral, velvety, violet-like with orris character; creamy, powdery top notes transitioning to woody, dry-fruity base; characteristic Parma violet and iris root facets with subtle leather and beeswax undertones

• ⚗️ Uses — Fine fragrance (floral, chypre, oriental compositions), orris and violet reconstructions, modifier and volume enhancer in woody-floral accords, luxury perfumery, cosmetic fragrances

• 🧴 Appearance — Colorless to pale straw-yellow, oily liquid

What is Methyl Ionone Gamma A?

Methyl ionone gamma A represents a specific commercial blend within the methyl ionone family, comprising multiple structural isomers with the molecular formula C₁₄H₂₂O. This material belongs to the ionone class of fragrance ingredients—cyclic terpenoid ketones originally derived from carotenoid degradation, though now produced exclusively through synthetic routes (Arctander, 1960; Sell, 2006).

The designation "gamma A" indicates a particular isomeric composition optimized for specific olfactory characteristics, with α-isomethyl ionone (CAS 127-51-5) typically constituting 60-70% of the mixture. This predominance of the α-isomethyl ionone isomer, characterized by its superior violet-orris character compared to other methylionone isomers, distinguishes gamma formulations from alpha or beta methylionone products.

Chemically, methylionones are characterized by a trimethylcyclohexenyl ring system attached to a pentenone or butenone side chain, with the specific position of double bonds and methyl group attachments determining the distinct olfactory properties of each isomer. Unlike simple ionones (C₁₃H₂₀O), methylionones possess an additional methyl substituent on the side chain, providing enhanced substantivity and modified olfactory profiles particularly valued in orris-type compositions.

The "A" suffix in commercial nomenclature typically denotes a premium or refined grade with controlled isomeric composition and superior olfactory performance characteristics compared to standard industrial methylionone mixtures.

Historical Background

The ionone family represents one of the earliest and most significant achievements in synthetic fragrance chemistry. β-Ionone was first synthesized by Ferdinand Tiemann and Paul Krüger in 1893, marking a milestone in the ability to recreate natural floral odors through synthetic means (Sell, 2006). This breakthrough enabled perfumers to access violet and iris notes without reliance on costly and inconsistent natural extracts.

The development of methylionone variants followed in the early 20th century as chemists explored structural modifications to the ionone scaffold. By introducing an additional methyl group to the side chain, researchers discovered compounds with enhanced tenacity, modified olfactory profiles, and superior performance in certain floral compositions—particularly in recreating the expensive and highly valued scent of orris root (Iris pallida, Iris germanica).

Key historical milestones:

• 1893: First synthesis of β-ionone by Tiemann and Krüger

• Early 1900s: Development of methylionone variants through structural modifications of the ionone framework

• Mid-20th century: Commercial production and optimization of isomeric mixtures for specific olfactory profiles

• 1960s-1970s: Recognition of α-isomethyl ionone as the most powerful and elegant isomer for orris reconstructions

• Late 20th century: Establishment of standardized commercial blends (e.g., "Gamma," "Alpha Extra," "Coeur" designations) by major fragrance houses

The material gained particular prominence in luxury perfumery during the mid-to-late 20th century, becoming essential in violet-type compositions and serving as a cornerstone ingredient in orris reconstructions—significantly more economical than natural iris concrete or absolute, which require vast quantities of rhizomes and extended aging periods.

Contemporary methylionone gamma formulations represent refined versions of these early synthetics, with controlled isomeric ratios optimized through advanced separation and cyclization techniques.

Olfactory Profile

Scent Family

Methyl ionone gamma A belongs to the floral-woody family, specifically classified as a violet-orris type fragrance material with powdery-cosmetic undertones.

Main Descriptors

The olfactory character of methyl ionone gamma A presents a sophisticated, multifaceted profile that evolves significantly from initial impression through dry-down:

Primary facets:

• Floral-violet: Characteristic Parma violet sweetness with refined elegance

• Orris-root: Dry, powdery iris rhizome character with earthy-rooty undertones

• Creamy-velvety: Smooth, luxurious texture particularly evident in top notes

Secondary facets:

• Woody-dry: Cedar-like, dry-woody base notes

• Fruity: Subtle dried-fruit nuances, occasionally described as plum-like

• Powdery-cosmetic: Classic face-powder, lipstick-like associations

Tertiary facets:

• Leather: Faint suede-like, almost animalic undertones at higher concentrations

• Beeswax: Warm, waxy facets contributing to depth and naturalness

• Earthy-rooty: Authentic rhizome character reminiscent of natural orris

The material's olfactory profile is notably cleaner and more refined than β-methylionone, which tends toward woody-cedarwood territories with less floral elegance. The predominance of α-isomethyl ionone in gamma formulations provides the characteristic smooth, velvety violet quality that made this isomer historically valuable.

Intensity

Methyl ionone gamma A demonstrates medium to strong olfactory impact, with intensity varying based on concentration and surrounding compositional elements. Individual isomers within the mixture exhibit significantly different odor thresholds—α-isomethyl ionone being notably more powerful than other methylionone isomers.

At typical usage levels (1-10% in compound), the material provides substantial presence without overwhelming delicate floral notes. Its intensity can be modulated through:

• Concentration adjustment (effective range: 0.5-25% in fragrance concentrate)

• Blending with woody-amber bases (which moderate violet intensity)

• Combination with salicylates and terpene alcohols (which soften powdery character)

Tenacity

Exceptional persistence characterizes methyl ionone gamma A, with documented longevity exceeding 124 hours on perfumer's strips at standard evaluation concentrations (10% in ethanol). This remarkable substantivity derives from:

• Relatively high molecular weight (206.33 g/mol)

• Hydrophobic character (log Kow 4.84)

• Low vapor pressure (0.005 mmHg at 20°C)

The material's tenacity makes it valuable as both a characterizing ingredient and a fixative component, particularly in:

• Orris-violet reconstructions requiring sustained floral presence

• Woody-floral bases demanding long-lasting bloom

• Cosmetic fragrances where persistent powdery notes are desired

Volatility

Methyl ionone gamma A functions primarily in the heart to base note register, with initial diffusion providing immediate violet impact that evolves into sustained woody-powdery persistence. The material's volatility profile (boiling point 238-266°C at 101.3 kPa) positions it as a semi-volatile ingredient with:

• Initial phase (0-30 minutes): Creamy-floral violet notes with orris character

• Development phase (30 minutes - 6 hours): Evolution into woody-powdery territory with enhanced earthy-rooty facets

• Dry-down phase (6+ hours): Sustained woody-powdery base with subtle leather and beeswax nuances

Fixative Role

While not classified as a traditional base-note fixative in the manner of musks or resins, methyl ionone gamma A contributes significant holding power and substantivity to fragrance compositions. Its fixative properties manifest through:

• Stabilization of volatile florals: Extends longevity of ephemeral violet, rose, and jasmine notes

• Bridging function: Links volatile citrus-floral top notes to heavier woody-ambery bases

• Structural reinforcement: Provides backbone to floral-oriental and chypre compositions

• Enhancement of other fixatives: Synergizes with woody materials (cedarwood, sandalwood, vetiver) and balsamic notes

Applications in Fine Fragrance

Methyl ionone gamma A occupies a distinguished position in contemporary luxury perfumery, serving both as a characterizing ingredient and as a sophisticated modifier. The material finds extensive application across multiple fragrance categories:

Violet and Orris Compositions

The material represents the cornerstone of modern violet-type perfumery, providing authentic Parma violet character while simultaneously delivering the dry, earthy, powdery facets associated with natural orris concrete. In these compositions, methyl ionone gamma A typically comprises 15-40% of the fragrance concentrate, often combined with:

• α-Ionone and β-ionone: For additional floral complexity and vintage violet character

• Orris butter or absolute (when budget permits): For naturalness and depth

• Cassie absolute, mimosa: For honeyed-powdery floral effects

• Iris pallida: When seeking premium natural reinforcement

Classic examples utilizing prominent methylionone notes include vintage violet fragrances and contemporary orris-centric compositions where the ingredient provides both top-note bloom and sustained dry-down presence.

Chypre and Floriental Structures

In chypre constructions, methyl ionone gamma A serves a dual role:

1. Floral enhancement: Rounds and softens oakmoss-patchouli bases

2. Powdery-dry modifier: Introduces cosmetic elegance bridging citrus-floral top notes and woody-mossy bases

The material pairs particularly effectively with:

• Oakmoss products, tree moss: Creating classic floral-mossy chypres

• Labdanum, benzoin: In ambery-oriental-chypre hybrids

• Rose otto, geranium: For floral-chypre compositions

• Bergamot, clary sage: Supporting herbaceous-aromatic dimensions

Typical usage: 5-15% of fragrance concentrate in chypre bases.

Woody-Leather Accords

The subtle leather and beeswax facets present in methyl ionone gamma A make it valuable in suede-type and woody-leather compositions, where it contributes:

• Powdery-soft leather effects: As opposed to harsh, birch tar-type leather notes

• Warmth and depth: In sandalwood-cedar-vetiver frameworks

• Cosmetic elegance: Softening aggressive woody-amber bases

Particularly effective combinations include:

• Vetiver oils (Haiti, Java): The material softens sharp, green, earthy edges

• Cedarwood (Atlas, Virginian): Enhancing dry-woody character with floral polish

• Sandalwood, Javanol: Creating creamy-woody effects with powdery overtones

• Leather bases (isobutyl quinoline, birch tar): Providing soft, suede-like refinement

Salicylate-Floral Systems

Methyl ionone gamma A demonstrates remarkable synergy with benzyl salicylate and related compounds, creating voluminous, diffusive, floral-cosmetic effects particularly valued in:

• Lily-type compositions: Where the material enhances waxy-green-floral effects

• Ylang-ylang reconstructions: Adding powdery-creamy depth to indolic florals

• Tuberose-narcissus bases: Introducing earthy-powdery facets

• Cosmetic-aldehydic florals: Providing substantivity and orris refinement

The combination of methylionone + salicylates + musks represents a classic structural element in many prestige feminine fragrances, delivering the characteristic smooth, enveloping, diffusive quality associated with luxury floral perfumery.

Performance in Formula

Methyl ionone gamma A exhibits predictable and reliable performance characteristics in fragrance formulations:

Blending Behavior: The material demonstrates excellent compatibility with most perfumery ingredients, showing particular affinity for:

• Woody materials (cedarwood, sandalwood, vetiver, patchouli)

• Floral absolutes and essential oils (rose, jasmine, ylang-ylang, neroli)

• Salicylates and benzoates

• Synthetic musks (galaxolide, ambrettolide, macrocyclic musks)

• Ambery bases and balsams

Some caution is advised when combining with highly aldehydic or very green notes, as the powdery-floral character may dampen freshness if used at excessive concentrations.

Typical Usage Levels:

• Orris-violet focused compositions: 15-40%

• Floral modifiers in complex accords: 3-15%

• Woody-floral bases: 5-20%

• Chypre and oriental structures: 3-12%

• Functional fragrances: 2-8%

Stability Considerations: Methyl ionone gamma A demonstrates excellent stability in alcoholic solutions and across most product matrices:

• Alcoholic perfumes: Excellent stability, no discoloration

• Emulsions (creams, lotions): Stable across typical pH ranges (4-8)

• Soaps: Some potential for reaction at very high pH (>11); use with caution in hot-process soaps

• Detergents and cleaners: Generally stable though some odor attenuation may occur

Light sensitivity: Minimal photodegradation; suitable for products in clear glass packaging

Oxidation resistance: Good stability; no significant autoxidation issues under normal storage conditions

Solubility:

• Excellent in ethanol, diethyl phthalate, isopropyl myristate

• Soluble in 8 volumes of 70% ethanol

• Limited water solubility (as expected for lipophilic materials)

Industrial & Technical Uses

Beyond fine fragrance applications, methyl ionone gamma A serves functional purposes across multiple industries:

Cosmetics and Personal Care

• Face powders and compacts: Reinforces cosmetic-powdery character

• Lipsticks and lip products: Contributes signature cosmetic-floral notes

• Creams and lotions: Provides elegant floral-powdery dry-down

• Shampoos and hair care: Imparts long-lasting floral-orris notes with good substantivity on hair

• Deodorants: Creates sophisticated floral-fresh effects with tenacity

Functional Fragrances

• Fabric softeners: Delivers persistent floral-powdery notes on textiles

• Laundry detergents: Provides floral-fresh effects with reasonable performance through wash cycle

• Air fresheners: Contributes elegant floral notes with good diffusion characteristics

• Household cleaners: When floral-cosmetic signatures are desired (though usage may be limited by cost)

Flavor Applications

Minor use in flavor formulations (FEMA 2711 approved), particularly in:

• Floral-fruity candy flavors

• Violet and orris mimetics for confectionery

• Specialty fruit flavors requiring violet-berry notes

Note: Flavor usage is limited compared to perfumery applications due to the distinct, somewhat soapy taste profile that is less universally appreciated in food contexts.

Regulatory & Safety Overview

IFRA Status

Methyl ionone (mixed isomers) is subject to quantitative restrictions under IFRA Standards (Amendment 49, revised 2020; confirmed in Amendment 51, 2023). The material has specific maximum concentration limits based on dermal sensitization considerations:

Maximum acceptable concentrations in finished consumer products:

The above limits apply to methyl ionone isomers used individually or in combination.

IFRA Standards Library: https://ifrafragrance.org/standards/IFRA_STD_063.pdf

EU Cosmetics Regulation

Under EU Regulation (EC) No 1223/2009 (Annex III), α-isomethyl ionone (the predominant component of methyl ionone gamma A) is listed among the 26 declarable fragrance allergens:

Labeling requirements:

• Leave-on products: Must be declared if present ≥ 0.001% (10 ppm)

• Rinse-off products: Must be declared if present ≥ 0.01% (100 ppm)

Labeling format: List "Alpha-Isomethyl Ionone" in the INCI ingredient declaration

This allergen status applies specifically to α-isomethyl ionone (CAS 127-51-5), which constitutes approximately 60-70% of methyl ionone gamma A formulations. Manufacturers using this material in cosmetic products must ensure proper allergen declaration on product labels when thresholds are exceeded.

FEMA Status

Methyl ionone mixture is approved for flavor use:

• FEMA Number: 2711

• Status: GRAS (Generally Recognized As Safe) when used in accordance with good manufacturing practices

• Individual isomers may have separate FEMA designations (e.g., FEMA 2712, 2714)

Flavor applications remain minor relative to perfumery usage.

Toxicology

The safety profile of methyl ionone has been extensively evaluated by the Research Institute for Fragrance Materials (RIFM) and the Expert Panel for Fragrance Safety:

Acute Toxicity:

• Oral LD₅₀ (rat): >5,000 mg/kg (RIFM, 1973; Lalko et al., 2007)

• Dermal LD₅₀: Expected to be >5,000 mg/kg based on structural analogues

• Classification: Low acute toxicity

Dermal Sensitization:

• Recognized dermal sensitizer at certain exposure levels

• IFRA restrictions derived from quantitative risk assessment (QRA2 methodology)

• Human Repeated Insult Patch Test (HRIPT) data indicate sensitization potential at higher concentrations

• No Observed Effect Level (NOEL) established through guinea pig maximization tests

Skin Irritation:

• Mild to non-irritating at use concentrations

• Potential for irritation at concentrations significantly above recommended levels

Eye Irritation:

• Mild to moderate eye irritant potential (undiluted material)

• Appropriate caution advised in products with potential eye contact

Phototoxicity/Photoallergenicity:

• No evidence of phototoxic or photoallergenic potential

Systemic Toxicity:

• Low systemic toxicity based on repeated dose studies

• No evidence of reproductive or developmental toxicity at relevant exposure levels

• No mutagenic or genotoxic concerns identified

Environmental Profile:

• Log Kow: 4.84 (indicates moderate bioaccumulation potential)

• Biodegradability: Expected to be readily biodegradable based on structural characteristics

• Aquatic toxicity: Moderate toxicity to aquatic organisms; requires appropriate risk management in rinse-off applications

Natural Occurrence

Unlike the parent ionones (α, β, γ-ionone), which occur naturally as carotenoid degradation products in various plants, methylionones are not definitively confirmed natural constituents of essential oils or plant materials. While some historical literature suggests possible natural occurrence, this remains disputed and unconfirmed by modern analytical techniques (Sell, 2006).

The structural similarity to naturally occurring ionones suggests that methylionones could theoretically form through analogous biosynthetic pathways involving carotenoid breakdown and subsequent methylation reactions. However, if present in nature, concentrations would be trace and unlikely to be economically extractable.

Confirmed natural ionone sources (for context):

• Rosa damascena (Bulgarian rose oil): Contains β-damascone and β-ionone

• Viola odorata (Violet): Contains ionones contributing to characteristic scent

• Various Boronia species: Minor ionone constituents

• Osmanthus species: β-ionone and related compounds

The absence of economically viable natural sources has led to exclusive reliance on synthetic production for all commercial methylionone materials.

Production Methods

Methyl ionone gamma A, like all commercial methylionones, is produced through synthetic routes involving multi-step processes analogous to ionone synthesis. Production involves:

Step 1: Pseudocompound Formation

The synthesis begins with preparation of a linear "pseudomethylionone" precursor through aldol-type condensation:

Route A: From Citral

• Reactants: Citral (or 6-methylcitral) + methyl ethyl ketone

• Catalyst: Alkaline catalysts (NaOH, KOH) for n-methylpseudoionone; quaternary ammonium bases for isomethylpseudoionone

• Product: Mixture of n-methylpseudoionone and isomethylpseudoionone as geometric isomers (cis/trans)

Route B: From Dehydrolinalool (Modern industrial preference)

• Reactants: Dehydrolinalool + appropriate α,β-unsaturated ketone or enol ether of methyl ethyl ketone

• Advantage: Direct access from synthetic terpene alcohol; avoids citral dependence

• Product: Predominantly isomethylpseudoionone when using appropriate catalysis

The ratio of linear (n-methyl) to branched (isomethyl) pseudocompound isomers depends critically on catalyst choice and reaction conditions, directly influencing the final methylionone isomer distribution.

Step 2: Cyclization to Methylionones

The pseudomethylionone undergoes acid-catalyzed cyclization to form the trimethylcyclohexenyl ring system:

Cyclization catalysts:

• Concentrated sulfuric acid (85-98%): Produces primarily α-methylionone with some β-isomer

• Phosphoric acid (85%): Yields β-methylionone in higher proportion

• Boron trifluoride etherate (BF₃·Et₂O): In DMF solvent, produces γ-methylionone alongside α and β isomers

• Lewis acids (AlCl₃, ZnCl₂): Alternative catalysts with varying selectivities

The cyclization mechanism involves protonation of the terminal double bond, electrophilic attack on the trisubstituted double bond, and subsequent ring closure with simultaneous formation of the conjugated enone system.

Step 3: Isomer Separation and Blending

Following cyclization, the crude product contains multiple methylionone isomers (α, β, γ forms, each potentially as multiple geometric and optical isomers). Industrial processing involves:

Fractional distillation:

• High-efficiency columns separate isomers based on boiling point differences

• α-methylionone: bp ~97°C @ 0.35 kPa

• β-methylionone: bp ~102°C @ 0.35 kPa

• α-isomethylionone: bp ~130-131°C @ 1.3 kPa

• β-isomethylionone: bp ~94°C @ 0.4 kPa

Controlled blending: Commercial products like "Methyl Ionone Gamma A" represent carefully formulated blends of specific isomers (primarily α-isomethyl ionone at 60-70%, with controlled proportions of complementary isomers) to achieve desired olfactory profiles. Different suppliers and trade names (Iralia®, Isoraldeine, etc.) reflect varying isomeric compositions optimized for specific applications.

Modern Industrial Variations

Contemporary production may incorporate:

• Continuous flow reactors for pseudocompound formation

• Advanced separation technologies (preparative chromatography for high-purity specialty grades)

• Enantioselective synthesis methods (for research and premium applications, though commercial methylionones are racemic mixtures)

• Green chemistry approaches utilizing heterogeneous catalysis and reduced solvent systems

Major Producers

Global production of methylionones (all commercial grades) occurs at major fragrance houses and specialized aroma chemical manufacturers, including IFF, Givaudan, Firmenich, Symrise, and dedicated chemical companies supplying the fragrance industry.

References

• Arctander, S. (1960). Perfume and flavor materials of natural origin. Elizabeth, NJ: Arctander.

• European Commission. (2009). Regulation (EC) No 1223/2009 of the European Parliament and of the Council of 30 November 2009 on cosmetic products (Annex III: List of substances which cosmetic products must not contain except subject to the restrictions laid down). Official Journal of the European Union.

• International Fragrance Association. (2020). IFRA Standard: Methyl ionone, mixed isomers (Amendment 49). Retrieved from https://ifrafragrance.org/standards/IFRA_STD_063.pdf

• International Fragrance Association. (2023). IFRA Standards—51st Amendment. Retrieved from https://ifrafragrance.org/standards-library

• Lalko, J., Lapczynski, A., McGinty, D., Bhatia, S. P., Letizia, C. S., & Api, A. M. (2007). Fragrance material review on methyl ionone (mixture of isomers). Food and Chemical Toxicology, 45(Suppl. 1), S235-S240. https://doi.org/10.1016/j.fct.2007.09.054

• Rowe, D. J. (Ed.). (2005). Chemistry and technology of flavors and fragrances. Oxford: Blackwell Publishing.

• Sell, C. S. (2006). The chemistry of fragrances: From perfumer to consumer (2nd ed.). Cambridge: Royal Society of Chemistry.

• Sigma-Aldrich. (2025). Methyl ionone (mixture of isomers) [Product specifications]. Retrieved from https://www.sigmaaldrich.com

• U.S. Food and Drug Administration. (2024). FEMA GRAS Assessment: Methyl ionone (FEMA 2711). Flavor and Extract Manufacturers Association.