Science Fair Project Encyclopedia
Ionone or 4-(2,6,6-trimethyl-1-cyclohexen-1-yl)-3-Buten-2-one or cyclocitrylideneacetone or irisone C13H20O is a chemical substance and part of the terpene family. Ionone is a aroma compound. It is a pale yellow liquid with a woody, dry, fruity, raspberry and violet smell. It is a raw material for the production of retinol
Beta ionone (left) has a less pronounced odor than alpha ionone (right).
The nucleophilic addition of the carbanion 3 of acetone 1 to the carbonylgroup on citral 4 is base catalysed. The aldol condensation product 5 eliminates water throught the enolate ion 6 to the pseudoionone 7.
The reaction proceeds by acid catalysis where the double bond in 7 opens to form the carbocation 8. A rearrangement reaction of the carbocation follows with ring closure to 9. Finally a hydrogen atom can be abstracted from 9 by a acceptor molecule (Y) to form either 10 (extended conjugated system) or 11.
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