Ionone
1771473
224813215
2008-07-10T15:08:22Z
148.177.1.218
redundant
{{Chembox new
| Name = Ionones
| ImageFileL1 = alpha-ionone-label.png
| ImageNameL1 = alpha-ionone
| ImageSizeL1 = 120px
| ImageFileR1 = beta-ionone-label.png
| ImageNameR1 = beta-ionone
| ImageSizeR1 = 120px
| ImageFile2 = gamma-ionone-label.png
| ImageName2 = gamma-ionone
| ImageSize2 = 120px
| IUPACName = α: (3''E'')-4-(2,6,6-Trimethylcyclohex-2-en-1-yl)but-3-en-2-one<br />β: (3''E'')-4-(2,6,6-Trimethylcyclohex-1-en-1-yl)but-3-en-2-one<br />γ: (3''E'')-4-(2,2-Dimethyl-6-methylenecyclohexyl)but-3-en-2-one
| OtherNames = Cyclocitrylideneacetone, irisone, jonon
| Section2 = {{Chembox Properties
| Formula = C<sub>13</sub>H<sub>20</sub>O
| MolarMass = 192.30 g/mol
| Density = α: 0.933 g/cm<sup>3</sup><br />β: 0.945 g/cm<sup>3</sup>
| MeltingPt = β: -49 °C
| BoilingPt = β: 126-128 °C at 12 mmHg
| CASOther = α: 127-41-3<br />β: 79-77-6<br />γ: 79-76-5
| SMILES = α: C\C1=C\CCC(C)(C)C1/C=C/C(C)=O<br />β: CC1(C)CCCC(\C)=C1\C=C\C(C)=O<br />γ: C=C1CCCC(C)(C)C1/C=C/C(C)=O}}
}}
The '''ionones''' are a series of closely related [[chemical substance]]s that are part of a group of compounds known as rose ketones, which also includes [[damascone]]s and [[damascenone]]s. Ionones are [[aroma compound]]s found in a variety of [[essential oil]]s, 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.<ref>[http://www.leffingwell.com/rose.htm Rose (Rosa damascena)], John C. Leffingwell</ref> ''beta''-Ionone is also a raw material for the production of [[retinol]]. Biochemically, the ionones are derived from the degradation of [[carotenoid]]s.
==Organic synthesis==
Ionone can be [[organic synthesis|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]].<ref>{{cite journal | author=NODA, C., ALT, G. P., WERNECK, R. M. et al. |title=Aldol Condensation of Citral with Acetone on Basic Solid Catalysts|journal=Braz. J. Chem. Eng. |year=1998 |volume =15 |issue=2 |url= http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66321998000200004 |doi=10.1590/S0104-66321998000200004}}</ref><ref>{{cite journal| title= Pseudoionone |author=Alfred Russell and R. L. Kenyon |journal=[[Organic Syntheses]], Coll. Vol. 3 |volume=23 |pages=78 |url=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}}</ref>
The [[nucleophilic addition]] of the [[carbanion]] '''3''' of acetone '''1''' to the [[carbonyl]]group on citral '''4''' is [[base (chemistry)|base]] [[catalysis|catalysed]]. The [[aldol condensation]] product '''5''' [[elimination reaction|eliminates]] water through the [[enolate ion]] '''6''' to the pseudoionone '''7'''.
[[Image:iononone3.gif]]
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'''.
[[Image:ionone4.gif]]
==References==
{{reflist}}
[[Category:perfume ingredients]]
[[Category:flavors]]
[[Category:Ketones]]
[[Category:Terpenes and terpenoids]]
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