Geraniol is a monoterpenoid and an

alcohol Alcohol most commonly refers to: * Alcohol (chemistry), an organic compound in which a hydroxyl group is bound to a carbon atom * Alcohol (drug), an intoxicant found in alcoholic drinks Alcohol may also refer to: Chemicals * Ethanol, one of sev ...

. 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 water, but it is soluble in common organic solvents. The functional group derived from geraniol (in essence, geraniol lacking the terminal −OH) is called geranyl.

Uses and occurrence

In addition to rose oil, palmarosa oil, and citronella oil, it also occurs in small quantities in

geranium ''Geranium'' is a genus of 422 species of annual, biennial, and perennial plants that are commonly known as geraniums or cranesbills. They are found throughout the temperate regions of the world and the mountains of the tropics, but mostly in ...

, lemon, and many other

essential oil An essential oil is a concentrated hydrophobic liquid containing volatile (easily evaporated at normal temperatures) chemical compounds from plants. Essential oils are also known as volatile oils, ethereal oils, aetheroleum, or simply as the o ...

s. With a rose-like scent, it is commonly used in perfumes. It is used in flavors such as peach,

raspberry The raspberry is the edible fruit of a multitude of plant species in the genus ''Rubus'' of the rose family, most of which are in the subgenus '' Idaeobatus''. The name also applies to these plants themselves. Raspberries are perennial with w ...

grapefruit The grapefruit (''Citrus'' × ''paradisi'') is a subtropical citrus tree known for its relatively large, sour to semi-sweet, somewhat bitter fruit. The interior flesh is segmented and varies in color from pale yellow to dark pink. Grapefruit is ...

, red apple,

plum A plum is a fruit of some species in ''Prunus'' subg. ''Prunus'.'' Dried plums are called prunes. History Plums may have been one of the first fruits domesticated by humans. Three of the most abundantly cultivated species are not found i ...

, lime, orange, lemon, watermelon, pineapple, and

blueberry Blueberries are a widely distributed and widespread group of perennial flowering plants with blue or purple berries. They are classified in the section ''Cyanococcus'' within the genus ''Vaccinium''. ''Vaccinium'' also includes cranberries, bi ...

. Geraniol is produced by the

scent glands Scent gland are exocrine glands found in most mammals. They produce semi-viscous secretions which contain pheromones and other semiochemical compounds. These odor-messengers indicate information such as status, territorial marking, mood, and sexu ...

of honeybees to mark nectar-bearing flowers and locate the entrances to their hives. It is also commonly used as an insect repellent, especially for mosquitoes. The scent of geraniol is reminiscent of, but chemically unrelated to, 2-ethoxy-3,5-hexadiene, also known as geranium taint, a wine fault resulting from fermentation of sorbic acid by lactic acid bacteria. Geraniol pyrophosphat is important in

biosynthesis Biosynthesis is a multi-step, enzyme-catalyzed process where substrates are converted into more complex products in living organisms. In biosynthesis, simple compounds are modified, converted into other compounds, or joined to form macromolecules. ...

of other terpenes such as myrcene and ocimene.

Reactions

In acidic solutions, geraniol is converted to the cyclic terpene

α-terpineol Terpineol is any of four isomeric monoterpenoids. Terpenoids are terpene that are modified by the addition of a functional group, in this case, an alcohol. Terpineols have been isolated from a variety of sources such as cardamom, cajuput oil, p ...

. The alcohol group undergoes expected reactions. It can be converted to the tosylate, which is a precursor to the chloride. Geranyl chloride also arises by the Appel reaction by treating geraniol with triphenylphosphine and carbon tetrachloride. It can be hydrogenated. It can be oxidized to the aldehyde

geranial Citral is an acyclic monoterpene aldehyde, and being a monoterpene, it is made of two isoprene units. Citral is a collective term which covers two geometric isomers that have their own separate names; the ''E''-isomer is named geranial (''trans' ...

Health and safety

Geraniol is classified as D2B (Toxic materials causing other effects) using the

Workplace Hazardous Materials Information System The Workplace Hazardous Materials Information System (WHMIS; french: links=no, Système d'information sur les matières dangereuses utilisées au travail, SIMDUT) is Canada's national workplace hazard communication standard. The key elements of t ...

(WHMIS).

History

Geraniol was first isolated in pure form in 1871 by the German chemist

Oscar Jacobsen Oscar Jacobsen (1 January 1850 – 6 August 1902) was a Norwegian engineer and politician for the Liberal Party. Personal life He was born in Vågå as the son of Johanne Georgine Jørgensen and her husband Nils Lauritz Severin Jacobsen. H ...

(1840–1889). Using distillation, Jacobsen obtained geraniol from an essential oil which was obtained from geranium grass ('' Andropogon schoenanthus'') and which was produced in India. The chemical structure of geraniol was determined in 1919 by the French chemist Albert Verley (1867–1959). The chemical structure of geraniol appears on p. 70.

References

External links