Citronellol, or dihydrogeraniol, is a natural acyclic mono

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

. Both

enantiomer In chemistry, an enantiomer ( /ɪˈnænti.əmər, ɛ-, -oʊ-/ ''ih-NAN-tee-ə-mər''; from Ancient Greek ἐνάντιος ''(enántios)'' 'opposite', and μέρος ''(méros)'' 'part') – also called optical isomer, antipode, or optical anti ...

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

citronella oil Citronella oil Citronella 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 geranio ...

s, including ''

Cymbopogon nardus ''Cymbopogon nardus'', common name citronella grass, is a species of perennial aromatic plant from the family Poaceae, originating in tropical Asia. It is the source of an essential oil known as citronella oil, which is widely used for its natura ...

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

rose A rose is either a woody perennial flowering plant of the genus ''Rosa'' (), in the family Rosaceae (), or the flower it bears. There are over three hundred species and tens of thousands of cultivars. They form a group of plants that can be ...

(18–55%) and ''

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

'' geraniums.

Preparation

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

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 reduce or saturate organic ...

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

nerol Nerol is a monoterpenoid alcohol found in many essential oils such as lemongrass and hops. It was originally isolated from neroli oil, hence its name. This colourless liquid is used in perfumery. Like geraniol, nerol has a sweet rose odor but it ...

over

copper chromite Copper chromite is an inorganic compound with the formula Cu2Cr2O5. It is a black solid that is used to catalyze reactions in organic synthesis. History The material was first described in 1908. The catalyst was developed in North America by Home ...

catalyst. Homogeneous catalysts are used for the production of enantiomers. Citronellene is also a precursor.

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 (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