Citronellol, or dihydrogeraniol, is a natural acyclic monoterpenoid. Both enantiomers occur in nature. (+)-Citronellol, which is found in citronella oils, including Cymbopogon nardus (50%), is the more common isomer. (−)-Citronellol is widespread, but particularly abundant in the oils of rose (18–55%) and Pelargonium geraniums.[1]
 (+)-Citronellol (left) and (−)-citronellol (right)
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 R-(+)-Citronellol
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 S-(−)-Citronellol
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| Names | |
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| IUPAC name
3,7-Dimethyloct-6-en-1-ol
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| Other names
(±)-β-Citronellol; Cephrol, Corol
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| Identifiers | |
3D model (JSmol)
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| 1362474 | |
| ChEBI | |
| ChEMBL | |
| ChemSpider | |
| ECHA InfoCard | 100.003.069 |
| EC Number |
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| KEGG | |
PubChem CID
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| UNII |
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CompTox Dashboard (EPA)
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| Properties | |
| C10H20O | |
| Molar mass | 156.269 g·mol−1 |
| Density | 0.855 g/cm3 |
| Boiling point | 225 °C (437 °F; 498 K) |
| Viscosity | 11.1 mPa s |
| Hazards | |
| GHS labelling: | |
 
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| Warning | |
| H315, H317, H319 | |
| P261, P264, P272, P273, P280, P302+P352, P305+P351+P338, P321, P332+P313, P333+P313, P337+P313, P362, P363, P391, P501 | |
| NFPA 704 (fire diamond) | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Preparation
editSeveral million kilograms of citronellol are produced annually. It is mainly obtained by partial hydrogenation of geraniol or nerol over copper chromite catalyst.[2] Hydrogenation of both C=C bonds using a nickel catalyst gives tetrahydrogeraniol, yet another commercial fragrance.[3]
Homogeneous catalysts have been investigated for the production of enantiomers.[4][5]
Uses
editCitronellol is used in perfumes and as a fragrance in cleaning products. In many applications, one of the enantiomers is preferred. It is a component of citronella oil, an insect repellant.[2]
Citronellol is used as a raw material for the production of rose oxide.[2][6] It is also a precursor to many commercial and potential fragrances such as citronellol acetate, citronellyl oxyacetaldehyde, citronellyl methyl acetal, and ethyl citronellyl oxalate.[2]
Health and safety
editThe United States FDA considers citronellol as generally recognized as safe (GRAS) for food use.[7] Citronellol is subject to restrictions on its use in perfumery,[8] as some people may become sensitised to it, but the degree to which citronellol can cause an allergic reaction in humans is disputed.[9][10]
In terms of dermal safety, citronellol has been evaluated as an insect repellent.[11]
See also
editReferences
edit- ^ Lawless, J. (1995). The Illustrated Encyclopedia of Essential Oils. ISBN 978-1-85230-661-8.
- ^ a b c d Sell, Charles S. (2006). "Terpenoids". Kirk-Othmer Encyclopedia of Chemical Technology. doi:10.1002/0471238961.2005181602120504.a01.pub2. ISBN 0471238961.
- ^ Panten, Johannes; Surburg, Horst (2015). "Flavors and Fragrances, 2. Aliphatic Compounds". Ullmann's Encyclopedia of Industrial Chemistry. pp. 1–55. doi:10.1002/14356007.t11_t01. ISBN 978-3-527-30673-2.
- ^ Morris, Robert H. (2007). "Ruthenium and Osmium". In De Vries, J. G.; Elsevier, C. J. (eds.). The Handbook of Homogeneous Hydrogenation. Weinheim: Wiley-VCH. ISBN 978-3-527-31161-3.
- ^ Ait Ali, M.; Allaoud, S.; Karim, A.; Roucoux, A.; Mortreux, A. (1995). "Catalytic Synthesis of (R)- and (S)-citronellol by homogeneous hydrogenation over amidophosphinephosphinite and diaminodiphosphine rhodium complexes". Tetrahedron: Asymmetry. 6 (2): 369. doi:10.1016/0957-4166(95)00015-H.
- ^ Alsters, Paul L.; Jary, Walther; Aubry, Jean-Marie (2010). ""Dark" Singlet Oxygenation of β-Citronellol: A Key Step in the Manufacture of Rose Oxide". Organic Process Research & Development. 14: 259–262. doi:10.1021/op900076g.
- ^ "Redirect". epa.gov. Retrieved 29 July 2015.
- ^ "Standards Restricted - IFRA International Fragrance Association". Archived from the original on 6 January 2012. Retrieved 19 July 2012.
- ^ "Cropwatch Report April 2008" (PDF). Archived from the original (PDF) on 10 February 2014. Retrieved 19 July 2012.
- ^ Survey and health assessment of chemical substances in massage oils Archived 27 September 2007 at the Wayback Machine
- ^ Taylor, W. G.; Schreck, C. E. (1985). "Chiral-phase capillary gas chromatography and mosquito repellent activity of some oxazolidine derivatives of (+)- and (−)-citronellol". Journal of Pharmaceutical Sciences. 74 (5): 534–539. doi:10.1002/jps.2600740508. PMID 2862274.