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unsaturated ketones of the cyclohexene series, with similar pleasant odors. Ionones are colorless liquids with high boiling point. They are readily soluble in alcohol. Ionones include Ionone proper as well as its homologs methylionone, isomethylionone, and irone. Ionones have several isomers, of which the a-isomers exhibit the most delicate and refined odors. In weak solutions, Ionone has the odor of violet, methylionone and isomethylionone have the odor of violet tinged with orris-root, and irone has the odor of orrisroot tinged with violet.
Ionone is contained in some fruit and essential oils. Methylionone and isomethylionone have not been found in nature, whereas irone is the main constituent (60–80 percent) of the essential oil prepared from orrisroot.
In industry, Ionone, methylionone, and isomethylionone are obtained from citral. Irone is obtained from methylcitral (usually in the form of isomer mixtures). Ionones are widely used in the production of perfumes and colognes and in the aromatization of cosmetics. /3-Ionone is also used in the production of vitamin A.