Citronellol Explained

Citronellol should not 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

• Citronellal
• Geraniol
• Rhodinol
• Pelargonium graveolens
• Perfume intolerance (allergy)

Notes and References

1. Book: Lawless, J. . The Illustrated Encyclopedia of Essential Oils . 978-1-85230-661-8. 1995 .
2. Book: 10.1002/0471238961.2005181602120504.a01.pub2. Terpenoids . Kirk-Othmer Encyclopedia of Chemical Technology . 2006 . Sell . Charles S. . 0471238961 .
3. Book: Morris, Robert H. . Ruthenium and Osmium . The Handbook of Homogeneous Hydrogenation . J. G. . De Vries . C. J. . Elsevier . 2007 . Wiley-VCH . Weinheim . 978-3-527-31161-3.
4. 10.1016/0957-4166(95)00015-H . Catalytic Synthesis of (R)- and (S)-citronellol by homogeneous hydrogenation over amidophosphinephosphinite and diaminodiphosphine rhodium complexes . 1995 . Ait Ali . M. . Allaoud . S. . Karim . A. . Roucoux . A. . Mortreux . A. . Tetrahedron: Asymmetry . 6 . 2 . 369.
5. "Dark" Singlet Oxygenation of β-Citronellol: A Key Step in the Manufacture of Rose Oxide . Organic Process Research & Development . 10.1021/op900076g . 14 . 2010 . 259–262 . Alsters . Paul L. . Jary . Walther . Aubry . Jean-Marie.
6. Web site: Redirect. epa.gov. 29 July 2015.
7. Web site: Standards Restricted - IFRA International Fragrance Association . 19 July 2012 . dead . https://web.archive.org/web/20120106222844/http://www.ifraorg.org/en-us/standards_restricted/s3/p3 . 6 January 2012 .
8. Web site: Cropwatch Report April 2008 . 19 July 2012 . https://web.archive.org/web/20140210163144/http://www.leffingwell.com/Cropwatch%20Claims%20Victory%20Over%2026%20Allergens.pdf . 10 February 2014 . dead .
9. http://www2.mst.dk/common/Udgivramme/Frame.asp?pg=http://www2.mst.dk/udgiv/publications/2006/87-7052-278-2/html/kap07_eng.htm Survey and health assessment of chemical substances in massage oils
10. Taylor . W. G. . Schreck . C. E. . Chiral-phase capillary gas chromatography and mosquito repellent activity of some oxazolidine derivatives of (+)- and (−)-citronellol . Journal of Pharmaceutical Sciences. 1985 . 74 . 5 . 534–539 . 10.1002/jps.2600740508 . 2862274.