Alpha Methyl Ionone Aroma Chemical
CAS# 7779-30-8 / 7779-30-8

Alpha Methyl Ionone is a synthetic ingredient that plays an important role in the fragrance industry. Chemically, it is called 5-(2,6,6-trimethyl-2-cyclohexen-1-yl)-4-penten-3-one, and it is also known by other names such as Methyl Ionone Alpha, Cetone Alpha, or Raldeine A, a high-quality trademark of Givaudan. On the market, Methyl Ionone is often a mixture of several isomers such as Alpha, Beta, and Gamma, but the Alpha isomer is consistently the most preferred because of its clearly expressed floral character. Unlike Ionone, which can be found in nature, Methyl Ionone is entirely a laboratory invention. Its history began shortly after the scientists Tiemann and Krüger discovered how to synthesize Ionone in 1893. By adding a methyl group to the Ionone structure, they created a pale yellow to yellow liquid with a softer scent, less harsh than typical Ionone, and strongly reminiscent of orris root. This advance made Alpha Methyl Ionone a key material in the early 20th century, enabling the creation of classic powdery and violet-floral fragrances without relying on the extremely expensive natural oils of orris root or violet.

Description

Belonging to the floral and woody families, Alpha Methyl Ionone operates from the heart to the base of a fragrance, serving as both a fixative and an odor modifier. Its scent blends sweet violet, powdery facets, dry woods, orris root, and a slight berry-like sweetness. Compared with Alpha Ionone, which has a fresher, greener nuance, Alpha Methyl Ionone feels denser, smoother, and more cosmetic-powder-like. With medium-high intensity and good diffusion, it offers strong longevity and helps tightly bind floral and woody notes together. In formulation, it is considered essential for building violet, iris (orris) effects and powdery accords. It also adds body and refinement to woody notes such as sandalwood and cedar, and it is a principal contributor to the characteristic scent of classic lipstick and face powder. In terms of pairing, blending Alpha Methyl Ionone with clove-like Eugenol yields the iconic carnation accord, famously at the core of Guerlain L’Heure Bleue. With rose, it creates a romantic French-style combination like YSL Paris. When combined with vetiver or cedarwood, it softens rough edges and produces a more luxurious woody effect. Because it is a stable liquid, it is commonly used directly without needing a solvent.

Applications

Its applications span widely from women’s fragrances in the Floral and Oriental families to men’s fragrances in the Woody Floral Musk family. In cosmetics, it is a standard odor profile for lipstick, face powder, and facial creams. In soaps and detergents, it is widely used thanks to its stability in alkaline environments and a more economical cost compared with natural materials. From a safety standpoint, Alpha Methyl Ionone-and Methyl Ionones in general-are restricted by IFRA due to their potential to cause skin sensitization. The maximum permitted level in Category 4 fine fragrance is often around 10–15%, depending on the specific isomer and the IFRA updates, though in practice perfumers typically use lower dosages to avoid an overly heavy effect. It is also included among the 26 EU fragrance allergens that require labeling, commonly appearing under the name Alpha-Isomethyl Ionone or Methyl Ionone. For quality preservation, this relatively stable material should be stored in a cool, dry place away from light. Commercially, Alpha Methyl Ionone appears in many well-known products such as Guerlain L’Heure Bleue (a nostalgic waxy-powder feel), Dior Fahrenheit (a masculine violet note blended with leather), and Lancôme Trésor (adding smoothness to rose and peach notes). Finally, the expert Steffen Arctander discussed this material in entry 2063 of Volume II of Perfume and Flavor Chemicals. He described Alpha-Methyl Ionone as a warm floral-woody material reminiscent of violet, noting that the Alpha isomer is generally regarded more highly than ionones for being smoother, less sharp, and more orris-like in the late drydown. He considered it one of the most versatile perfumery materials, able to blend with almost all fragrance ingredients except the most volatile citrus essential oils, and a standard component in lipstick fragrances.