Ionone

The ionone (also Ionone, stress on the second syllable: Jonone ) form a group of substances that includes the individual substances α -, β -, and γ -ionone and one of the terpenes. The substances have a violet -like odor and are widely-used natural substances that are found in many plants.

Occurrence

All three Jononarten have been found in oils of various plants, especially in berries, tea and tobacco. Violet oil contains about 22% α -ionone, β -ionone is found for example in the henna, the tamarind contains γ -ionone. β -ionone is a degradation product of β -carotene.

From α -ionone both optical isomers [(R) - α -ionone and (S) - α -ionone ] are found in nature.

An overview of the individual substances and their properties are in the following table.

• Violon
• (E)- Mega stigma -4 ,7 -diene- 9-one
• (E ) -4 - ( 2,6,6- trimethyl-2- cyclohexen-1 -yl) - 3-buten- 2-one

• Boronion
• (E)- Mega stigma -5 ( 13) ,7-dien- 9-one
• (E ) -4 - ( 2,6,6- trimethyl-1- cyclohexen-1 -yl) - 3-buten- 2-one

• (E)- Mega stigma -4 ,7 -diene- 9-one
• (E ) -4 - ( 2-methylene- 6 ,6 -dimethyl- cyclohexane-1- yl) - 3-buten- 2-one

• (R )-enantiomer: with veilchenartigem, himbeerartigem, flowery smell

• ( S)- enantiomer: with woody smell veilchenartigem

• [ α ] D23: 347 ° (D)
• [ α ] D25: 0 ° ( DL)
• [ α ] D27: -406 ° (L )

Production and representation

The ionone can be either from corresponding vegetable oils derived or synthetically produced.

1893 was developed by Wilhelm Haarmann for Haarmann & Reimer to a process for the synthesis of α - and β -ionone from citral and patented. After that citral is condensed in a basic medium with acetone. This results in pseudoionone.

This can be cyclized to a mixture of α - and β -ionone on heating with dilute acid.

Depending on the reaction conditions, the ratio of α -to β -ionone changes. In the cyclization with phosphoric acid is mainly α -ionone, β -ionone with sulfuric acid.

Through the implementation of pseudoionone with boron trifluoride and acetic acid can be concentrated at a high yield of pure β -ionone produced.

Ultraviolet radiation is normally present in the trans - configuration double bond of the side chain can be converted into the cis configuration.

Use

Ionone is mostly used in large quantities in the fragrance industry in floral or fantasy composition. Depending on the application are here isomer mixtures or individual isomers, which are all different in the fragrance used. Ionone are used to a lesser extent also for the production of flavors.

They also serve to produce the important in perfumery Damascenonen and Isomethyljononen.

β -ionone is also an important starting material for the production of retinol and carotenes.

Biological Significance

Ionone can still be smelled by humans at very low concentrations. For β -ionone, the odor threshold is 0.07 ppb in 10-7 mg per liter of air or 0.1 ppb, for (R)- γ -ionone at 11 ppb and (S)- γ -ionone.

Safety

The LD50 (rat, oral) is estimated for α -ionone at 4590 mg · kg -1 for β -ionone at 2920 mg · kg -1.

Jonone have an allergenic potential and should therefore be possible if handled with gloves.

α -ionone is also divided into the water hazard class 2 ( water polluting).