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 water, but it is soluble in common organic solvents. The

functional group In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the r ...

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, lemon, and many other essential oils. With a

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 ...

-like scent, it is commonly used in

perfume Perfume (, ; french: parfum) is a mixture of fragrant essential oils or aroma compounds (fragrances), fixatives and solvents, usually in liquid form, used to give the human body, animals, food, objects, and living-spaces an agreeable scent ...

s. It is used in flavors such as

peach The peach (''Prunus persica'') is a deciduous tree first domesticated and cultivated in Zhejiang province of Eastern China. It bears edible juicy fruits with various characteristics, most called peaches and others (the glossy-skinned, n ...

, raspberry, grapefruit, red apple, plum, lime, orange, lemon, watermelon, pineapple, and blueberry. Geraniol is produced by the scent glands 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 of other

terpene Terpenes () are a class of natural products consisting of compounds with the formula (C5H8)n for n > 1. Comprising more than 30,000 compounds, these unsaturated hydrocarbons are produced predominantly by plants, particularly conifers. Terpenes ...

s such as

myrcene Myrcene, or β-myrcene, is a monoterpene. A colorless oil, it occurs widely in essential oils. It is produced mainly semi-synthetically from ''Myrcia'', from which it gets its name. It is an intermediate in the production of several fragrances. � ...

and ocimene.

Reactions

In acidic solutions, geraniol is converted to the cyclic terpene

α-terpineol Terpineol is any of four isomeric monoterpene, monoterpenoids. Terpenoids are terpene that are modified by the addition of a functional group, in this case, an Alcohol (chemistry), alcohol. Terpineols have been isolated from a variety of sources ...

. 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 ...

(WHMIS).

History

Geraniol was first isolated in pure form in 1871 by the German chemist Oscar Jacobsen (1840–1889). Using

distillation Distillation, or classical distillation, is the process of separating the components or substances from a liquid mixture by using selective boiling and condensation, usually inside an apparatus known as a still. Dry distillation is the he ...

, 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