Not to be confused with Citronellal.

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 hydrogenation of geraniol or nerol over copper chromite catalyst.[2] Homogeneous catalysts are used for the production of enantiomers.[3][4]

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][5] 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.[6] Citronellol is subject to restrictions on its use in perfumery,[7] as some people may become sensitised to it, but the degree to which citronellol can cause an allergic reaction in humans is disputed.[8][9]

In terms of dermal safety, citronellol has been evaluated as an insect repellent.[10]

See also

References

  1. ^ Lawless, J. (1995). The Illustrated Encyclopedia of Essential Oils. ISBN 978-1-85230-661-8.
  2. ^ a b c d Sell, Charles S. (2006). "Terpenoids". Kirk-Othmer Encyclopedia of Chemical Technology. doi:10.1002/0471238961.2005181602120504.a01.pub2. ISBN 0471238961.
  3. ^ 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.
  4. ^ 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.
  5. ^ 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.
  6. ^ "Redirect". epa.gov. Retrieved 29 July 2015.
  7. ^ "Standards Restricted - IFRA International Fragrance Association". Archived from the original on 6 January 2012. Retrieved 19 July 2012.
  8. ^ "Cropwatch Report April 2008" (PDF). Archived from the original (PDF) on 10 February 2014. Retrieved 19 July 2012.
  9. ^ Survey and health assessment of chemical substances in massage oils Archived 27 September 2007 at the Wayback Machine
  10. ^ 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.