Citronellol

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]

Not to be confused with Citronellal.
Citronellol
Skeletal formula of (+)-citronellol and (−)-citronellol
(+)-Citronellol (left) and (−)-citronellol (right)
Ball-and-stick model of the (+)-citronellol molecule
R-(+)-Citronellol
Ball-and-stick model of the (−)-citronellol molecule
S-(−)-Citronellol
Names
IUPAC name
3,7-Dimethyloct-6-en-1-ol
Other names
(±)-β-Citronellol; Cephrol, Corol
Identifiers
3D model (JSmol)
1362474
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.003.069
EC Number
  • 247-737-6
KEGG
UNII
  • InChI=1S/C10H20O/c1-9(2)5-4-6-10(3)7-8-11/h5,10-11H,4,6-8H2,1-3H3 checkY
    Key: QMVPMAAFGQKVCJ-UHFFFAOYSA-N checkY
  • InChI=1/C10H20O/c1-9(2)5-4-6-10(3)7-8-11/h5,10-11H,4,6-8H2,1-3H3/t10-/m1/s1
    Key: QMVPMAAFGQKVCJ-SNVBAGLBBU
  • InChI=1/C10H20O/c1-9(2)5-4-6-10(3)7-8-11/h5,10-11H,4,6-8H2,1-3H3
    Key: QMVPMAAFGQKVCJ-UHFFFAOYAO
  • OCC[C@@H](CC/C=C(/C)C)C
  • C\C(C)=C\CCC(C)CCO
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:
GHS07: Exclamation markGHS09: Environmental hazard
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)
NFPA 704 four-colored diamond
1
2
0
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)
Infobox references

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. 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.
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