Geraniol is a monoterpenoid and an

alcohol Alcohol may refer to: Common uses * Alcohol (chemistry), a class of compounds * Ethanol, one of several alcohols, commonly known as alcohol in everyday life ** Alcohol (drug), intoxicant found in alcoholic beverages ** Alcoholic beverage, an alco ...

. It is the primary component of

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 ...

and is a primary component of

rose oil Rose oil (rose otto, attar of rose, attar of roses, or rose essence) is an essential oil that is extracted from the petals of various types of rose. ''Rose ottos'' are extracted through steam distillation, while ''rose absolutes'' are obtained t ...

and 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.

Uses and occurrence

In addition to being found in

, palmarosa oil, and

, 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, with the gre ...

lemon The lemon (''Citrus'' × ''limon'') is a species of small evergreen tree in the ''Citrus'' genus of the flowering plant family Rutaceae. A true lemon is a hybrid of the citron and the bitter orange. Its origins are uncertain, but some ...

, 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 ...

s. With a

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 ...

-like scent, it is commonly used in

perfume Perfume (, ) is a mixture of fragrance, fragrant essential oils or aroma compounds (fragrances), Fixative (perfumery), fixatives and solvents, usually in liquid form, used to give the human body, animals, food, objects, and living-spaces an agre ...

s and in scents such as

peach The peach (''Prunus persica'') is a deciduous tree first domesticated and Agriculture, cultivated in China. It bears edible juicy fruits with various characteristics, most called peaches and the glossy-skinned, non-fuzzy varieties called necta ...

raspberry The raspberry is the edible fruit of several plant species in the genus ''Rubus'' of the Rosaceae, rose family, most of which are in the subgenus ''Rubus#Modern classification, Idaeobatus''. The name also applies to these plants themselves. Ras ...

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

, red apple,

plum A plum is a fruit of some species in Prunus subg. Prunus, ''Prunus'' subg. ''Prunus'.'' Dried plums are often called prunes, though in the United States they may be labeled as 'dried plums', especially during the 21st century. Plums are ...

, lime, orange,

watermelon The watermelon (''Citrullus lanatus'') is a species of flowering plant in the family Cucurbitaceae, that has a large, edible fruit. It is a Glossary of botanical terms#scandent, scrambling and trailing vine-like plant, and is plant breeding ...

pineapple The pineapple (''Ananas comosus'') is a Tropical vegetation, tropical plant with an edible fruit; it is the most economically significant plant in the family Bromeliaceae. The pineapple is indigenous to South America, where it has been culti ...

, 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'' with the genus ''Vaccinium''. Commercial blueberries—both wild (lowbush) ...

. 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 ...

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 Sorbic acid, or 2,4-hexadienoic acid, is a natural organic compound used as a food preservative. It has the chemical formula and the structure . It is a colourless solid that is slightly soluble in water and sublimes readily. It was first iso ...

lactic acid bacteria Lactobacillales are an order of gram-positive, low-GC, acid-tolerant, generally nonsporulating, nonrespiring, either rod-shaped (bacilli) or spherical ( cocci) bacteria that share common metabolic and physiological characteristics. These bact ...

. Geranyl pyrophosphate is important in

biosynthesis Biosynthesis, i.e., chemical synthesis occurring in biological contexts, is a term most often referring to multi-step, enzyme-Catalysis, catalyzed processes where chemical substances absorbed as nutrients (or previously converted through biosynthe ...

of other

terpene Terpenes () are a class of natural products consisting of compounds with the formula (C5H8)n for n ≥ 2. Terpenes are major biosynthetic building blocks. Comprising more than 30,000 compounds, these unsaturated hydrocarbons are produced predomi ...

s such as

myrcene Myrcene, or β-myrcene, is a terpene, 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 frag ...

and ocimene. It is also used in the

pathway of many

cannabinoids Cannabinoids () are several structural classes of compounds found primarily in the ''Cannabis'' plant or as synthetic compounds. The most notable cannabinoid is the phytocannabinoid tetrahydrocannabinol (THC) (delta-9-THC), the primary psychoa ...

in the form of CBGA.

Reactions

acidic An acid is a molecule or ion capable of either donating a proton (i.e. hydrogen cation, H+), known as a Brønsted–Lowry acid, or forming a covalent bond with an electron pair, known as a Lewis acid. The first category of acids are the ...

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 oxidized to the aldehyde geranial. Hydrogenation of the two C=C bonds over a nickel catalyst gives tetrahydrogeraniol.

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; , SIMDUT) is Canada's national workplace hazard communication standard. The key elements of the system, which came into effect on October 31, 1988, are cautionary labelling of container ...

(WHMIS).

History

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

distillation Distillation, also classical distillation, is the process of separating the component substances of a liquid mixture of two or more chemically discrete substances; the separation process is realized by way of the selective boiling of the mixt ...

, Jacobsen obtained geraniol from an essential oil produced in India which was obtained from the so-called geranium grass. This essence, after which the compound was named, was a 50% cheaper substitute for the essence of the proper

flower with a similar, although less delicate, odor. 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