Chemistry:Citronellol

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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]

Preparation

Several 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

Citronellol 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

The 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

References

  1. ↑ Lawless, J. (1995). The Illustrated Encyclopedia of Essential Oils. ISBN 978-1-85230-661-8. 
  2. ↑ 2.0 2.1 2.2 2.3 Sell, Charles S. (2006). "Terpenoids". Kirk-Othmer Encyclopedia of Chemical Technology. doi:10.1002/0471238961.2005181602120504.a01.pub2. ISBN 0471238961. 
  3. ↑ 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. 
  4. ↑ Morris, Robert H. (2007). "Ruthenium and Osmium". in De Vries, J. G.; Elsevier, C. J.. The Handbook of Homogeneous Hydrogenation. Weinheim: Wiley-VCH. ISBN 978-3-527-31161-3. 
  5. ↑ 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. 
  6. ↑ 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. 
  7. ↑ "Redirect". epa.gov. http://www.epa.gov/pesticides/biopesticides/ingredients/factsheets/factsheet_167004.htm. Retrieved 29 July 2015. 
  8. ↑ "Standards Restricted - IFRA International Fragrance Association". Archived from the original on 6 January 2012. https://web.archive.org/web/20120106222844/http://www.ifraorg.org/en-us/standards_restricted/s3/p3. Retrieved 19 July 2012. 
  9. ↑ "Cropwatch Report April 2008". http://www.leffingwell.com/Cropwatch%20Claims%20Victory%20Over%2026%20Allergens.pdf. 
  10. ↑ Survey and health assessment of chemical substances in massage oils
  11. ↑ 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. https://zenodo.org/record/1229253. 



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