alpha-Irone

Title: a-Irone
CAS Registry Number: 79-69-6
CAS Name: 4-(2,5,6,6-Tetramethyl-2-cyclohexen-1-yl)-3-butene-2-one
Molecular Formula: C14H22O
Molecular Weight: 206.32
Percent Composition: C 81.50%, H 10.75%, O 7.75%
Literature References: Main perfume ingredient of violets. Both the d-(1,5)-cis- and d-(1,5)-trans-forms occur in nature. Isoln from irone mixture and synthesis: Naves, Helv. Chim. Acta 31, 893, 1103 (1948); Ruzicka et al., ibid. 31, 257 (1948). Synthesis: Barton, Mousseron-Canet, J. Chem. Soc. 1960, 271. Industrial preparation: Kaiser, Kimel, US 2877271 (1959 to Hoffmann-La Roche); Eschenmoser et al., US 3413351; US 3470241 (1968, 1969 to Firmenich & Cie). Nomenclature in early papers: Naves, Helv. Chim. Acta 32, 969 (1949). Stereochemistry: Tribolet, Schinz, ibid. 37, 2184 (1954); Naves, Ardizio, Bull. Soc. Chim. Fr. 1955, 1479; V. Rautenstrauch, G. Ohloff, Helv. Chim. Acta 54, 1776 (1971); V. Rautenstrauch et al., ibid. 67, 325 (1984). Stereoselective synthesis of cis- and trans-a-irones: S. Torii et al., J. Org. Chem. 45, 16 (1980); of (±)-cis-a-irone: C. Nussbaumer, G. Fráter, ibid. 52, 2096 (1987).
Properties: All forms are viscous liquids with characteristic odors.
Derivative Type: dl-cis-a-Irone
Properties: d420 0.9360; nD20 1.50098. uv max (ethanol): 227 nm (e 15400), Naves, Bachmann, Helv. Chim. Acta 32, 394 (1949).
Index of refraction: nD20 1.50098
Absorption maximum: uv max (ethanol): 227 nm (e 15400), Naves, Bachmann, Helv. Chim. Acta 32, 394 (1949)
Density: d420 0.9360
Derivative Type: d-cis-a-Irone
CAS Registry Number: 35124-13-1
Properties: [a]D20 +109° (CH2Cl2).
Optical Rotation: [a]D20 +109° (CH2Cl2)
Derivative Type: dl-trans-a-Irone
Properties: d420 0.9347; nD20 1.50119. uv max (ethanol): 229 (e 15450).
Index of refraction: nD20 1.50119
Absorption maximum: uv max (ethanol): 229 (e 15450)
Density: d420 0.9347
Derivative Type: d-trans-a-Irone
CAS Registry Number: 90242-81-2
Properties: [a]D20 +420° (CH2Cl2).
Optical Rotation: [a]D20 +420° (CH2Cl2)
alpha-Ketoglutaric Acid alpha-Latrotoxin alpha-L-Iduronidase alpha-Methylbenzylamine alpha-Methylene Butyrolactone


Irones are a group of methylionone odorants used in perfumery, derived from iris oil, e.g. orris root. The most commercially important of these are:

  • (-)-cis-γ-irone, and
  • (-)-cis-α-irone

Irones form through slow oxidation of triterpenoids in dried rhizomes of the iris species, Iris pallida. Irones typically have a sweet floral, iris, woody, ionone, odor.