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| Ionones | |
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| IUPAC name | α: (3E)-4-(2,6,6-Trimethylcyclohex-2-en-1-yl)but-3-en-2-one β: (3E)-4-(2,6,6-Trimethylcyclohex-1-en-1-yl)but-3-en-2-one γ: (3E)-4-(2,2-Dimethyl-6-methylenecyclohexyl)but-3-en-2-one |
| Other names | Cyclocitrylideneacetone, irisone, jonon |
| Properties | |
| Molecular formula | C13H20O |
| Molar mass | 192.30 g/mol |
| Density | α: 0.933 g/cm3 β: 0.945 g/cm3 |
| Melting point |
β: -49 °C |
| Boiling point |
β: 126-128 °C at 12 mmHg |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox references |
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The ionones are a series of closely related chemical substances that are part of a group of compounds known as rose ketones, which also includes damascones and damascenones. Ionones are aroma compounds found in a variety of essential oils, including rose oil. beta-Ionone is a significant contributor to the aroma of roses, despite its relatively low concentration, and is an important fragrance chemical used in perfumery.[1] beta-Ionone is also a raw material for the production of retinol. Biochemically, the ionones are derived from the degradation of carotenoids.
Organic synthesis
Ionone can be synthesised from citral and acetone with calcium oxide as a basic heterogeneous catalysis and serves as an example of an Aldol condensation followed by a rearrangement reaction.[2][3]
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 through 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 an acceptor molecule (Y) to form either 10 (extended conjugated system) or 11.
References
- ^ Rose (Rosa damascena), John C. Leffingwell
- ^ NODA, C., ALT, G. P., WERNECK, R. M. et al. (1998), "Aldol Condensation of Citral with Acetone on Basic Solid Catalysts", Braz. J. Chem. Eng. 15(2), doi:, <http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66321998000200004>
- ^ Alfred Russell and R. L. Kenyon, "Pseudoionone", Organic Syntheses, Coll. Vol. 3 23: 78, <http://www.orgsyn.org/orgsyn/default.asp?dbname=orgsyn&dataaction=search&metadata_directive=blind_gui&formgroup=quick_form_group&Preps.CollVol=3&Preps.CollPage=747&order_by=Preps.CollPage%20ASC>
Wikipedia content modification information:
- This page was last modified on 10 July 2008, at 15:08.
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