Citronellol, or dihydrogeraniol, is a natural acyclic mono

terpenoid The terpenoids, also known as isoprenoids, are a class of naturally occurring organic compound, organic chemicals derived from the 5-carbon compound isoprene and its derivatives called terpenes, diterpenes, etc. While sometimes used interchangeabl ...

. Both

enantiomer In chemistry, an enantiomer (Help:IPA/English, /ɪˈnænti.əmər, ɛ-, -oʊ-/ Help:Pronunciation respelling key, ''ih-NAN-tee-ə-mər''), also known as an optical isomer, antipode, or optical antipode, is one of a pair of molecular entities whi ...

s occur in nature. (+)-Citronellol, which is found in

citronella oil Citronella oilCitronella oil is an essential oil obtained from the leaves and stems of different species of '' Cymbopogon'' (lemongrass). The oil is used extensively as a source of perfumery chemicals such as citronellal, citronellol, and geran ...

s, including '' Cymbopogon nardus'' (50%), is the more common isomer. (−)-Citronellol is widespread, but particularly abundant in the oils of

rose A rose is either a woody perennial plant, perennial flowering plant of the genus ''Rosa'' (), in the family Rosaceae (), or the flower it bears. There are over three hundred Rose species, species and Garden roses, tens of thousands of cultivar ...

(18–55%) and ''

Pelargonium ''Pelargonium'' () is a genus of flowering plants that includes about 280 species of perennial plant, perennials, succulent plant, succulents, and shrubs, common name, commonly called geraniums, pelargoniums, or storksbills. ''Geranium'' is also ...

'' geraniums.

Preparation

Several million kilograms of citronellol are produced annually. It is mainly obtained by partial

hydrogenation Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to redox, reduce or Saturated ...

geraniol Geraniol is a monoterpenoid and an alcohol. It is the primary component of citronella oil and is a primary component of rose oil and palmarosa oil. It is a colorless oil, although commercial samples can appear yellow. It has low solubility i ...

or nerol over copper chromite catalyst. Hydrogenation of both C=C bonds using a nickel catalyst gives tetrahydro

, yet another commercial fragrance. Homogeneous catalysts have been investigated for the production of

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. Citronellol is used as a raw material for the production of rose oxide. It is also a precursor to many commercial and potential fragrances such as citronellol acetate, citronellyl oxyacetaldehyde, citronellyl methyl acetal, and ethyl citronellyl oxalate.

Health and safety

The United States FDA considers citronellol as

generally recognized as safe Generally recognized as safe (GRAS) is a United States Food and Drug Administration (FDA) designation that a chemical or substance added to food is considered safe by experts under the conditions of its intended use. An ingredient with a GRAS d ...

(GRAS) for food use. Citronellol is subject to restrictions on its use in perfumery, as some people may become sensitised to it, but the degree to which citronellol can cause an allergic reaction in humans is disputed. In terms of dermal safety, citronellol has been evaluated as an insect repellent.

References

{{Reflist Perfume ingredients Flavors Monoterpenes Alkenols

Preparation

Uses

Health and safety

See also

References