Geraniol
Encyclopedia
Geraniol is a monoterpenoid
and an alcohol
. It is the primary part of rose oil
, palmarosa oil, and citronella oil
(Java type). It also occurs in small quantities in geranium
, lemon
, and many other essential oil
s. It appears as a clear to pale-yellow oil that is insoluble in water, but soluble in most common organic solvents. It has a rose
-like odor and is commonly used in perfume
s. It is used in flavors such as peach, raspberry, grapefruit, red apple, plum, lime, orange, lemon, watermelon, pineapple, and blueberry.
s to help them mark nectar-bearing flowers and locate the entrances to their hives.
Although geraniol and other flavor compounds are found naturally in well-aged tobacco
, geraniol is listed in a 1994 report from cigarette companies as one of the 599 additives to cigarettes to improve their flavor.
based on geraniol (in essence, geraniol lacking the terminal -OH) is called geranyl. It is important in biosynthesis
of other terpene
s. It is a by-product of the metabolism of sorbate and, thus, is a very unpleasant contaminant of wine if bacteria are allowed to grow in wine.
.
Terpenoid
The terpenoids , sometimes called isoprenoids, are a large and diverse class of naturally occurring organic chemicals similar to terpenes, derived from five-carbon isoprene units assembled and modified in thousands of ways. Most are multicyclic structures that differ from one another not only in...
and an alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
. It is the primary part of rose oil
Rose oil
Rose oil, meaning either rose otto or rose absolute, is the essential oil extracted from the petals of various types of rose...
, palmarosa oil, and citronella oil
Citronella oil
Citronella oil is one of the essential oils obtained from the leaves and stems of different species of Cymbopogon. The oil is used extensively as a source of perfumery chemicals such as citronellal, citronellol and geraniol...
(Java type). It also occurs in small quantities in geranium
Pelargonium
Pelargonium is a genus of flowering plants which includes about 200 species of perennials, succulents, and shrubs, commonly known as scented geraniums or storksbills. Confusingly, Geranium is the correct botanical name of a separate genus of related plants often called Cranesbills. Both Geranium...
, lemon
Lemon
The lemon is both a small evergreen tree native to Asia, and the tree's ellipsoidal yellow fruit. The fruit is used for culinary and non-culinary purposes throughout the world – primarily for its juice, though the pulp and rind are also used, mainly in cooking and baking...
, and many other essential oil
Essential oil
An essential oil is a concentrated hydrophobic liquid containing volatile aroma compounds from plants. Essential oils are also known as volatile oils, ethereal oils or aetherolea, or simply as the "oil of" the plant from which they were extracted, such as oil of clove...
s. It appears as a clear to pale-yellow oil that is insoluble in water, but soluble in most common organic solvents. It has a rose
Rose
A rose is a woody perennial of the genus Rosa, within the family Rosaceae. There are over 100 species. They form a group of erect shrubs, and climbing or trailing plants, with stems that are often armed with sharp prickles. Flowers are large and showy, in colours ranging from white through yellows...
-like odor and is commonly used in perfume
Perfume
Perfume is a mixture of fragrant essential oils and/or aroma compounds, fixatives, and solvents used to give the human body, animals, objects, and living spaces "a pleasant scent"...
s. It is used in flavors such as peach, raspberry, grapefruit, red apple, plum, lime, orange, lemon, watermelon, pineapple, and blueberry.
Use
Research has shown geraniol to be an effective plant-based mosquito repellent. On the other hand, it can attract bees as it is produced by the scent glands of honey beeHoney bee
Honey bees are a subset of bees in the genus Apis, primarily distinguished by the production and storage of honey and the construction of perennial, colonial nests out of wax. Honey bees are the only extant members of the tribe Apini, all in the genus Apis...
s to help them mark nectar-bearing flowers and locate the entrances to their hives.
Although geraniol and other flavor compounds are found naturally in well-aged tobacco
Tobacco
Tobacco is an agricultural product processed from the leaves of plants in the genus Nicotiana. It can be consumed, used as a pesticide and, in the form of nicotine tartrate, used in some medicines...
, geraniol is listed in a 1994 report from cigarette companies as one of the 599 additives to cigarettes to improve their flavor.
Biochemistry
The functional groupFunctional group
In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. The same functional group will undergo the same or similar chemical reaction regardless of the size of the molecule it is a part of...
based on geraniol (in essence, geraniol lacking the terminal -OH) is called geranyl. It is important in biosynthesis
Biosynthesis
Biosynthesis is an enzyme-catalyzed process in cells of living organisms by which substrates are converted to more complex products. The biosynthesis process often consists of several enzymatic steps in which the product of one step is used as substrate in the following step...
of other terpene
Terpene
Terpenes are a large and diverse class of organic compounds, produced by a variety of plants, particularly conifers, though also by some insects such as termites or swallowtail butterflies, which emit terpenes from their osmeterium. They are often strong smelling and thus may have had a protective...
s. It is a by-product of the metabolism of sorbate and, thus, is a very unpleasant contaminant of wine if bacteria are allowed to grow in wine.
Reactions
In acidic solutions, geraniol is converted to the cyclic terpene alpha-terpineolTerpineol
Terpineol is a naturally occurring monoterpene alcohol that has been isolated from a variety of sources such as cajuput oil, pine oil, and petitgrain oil. There are three isomers, alpha-, beta-, and gamma-terpineol, the last two differing only by the location of the double bond...
.
Related compounds
- CitralCitralCitral, or 3,7-dimethyl-2,6-octadienal or lemonal, is either of, or a mixture of, a pair of terpenoids with the molecular formula C10H16O. The two compounds are double bond isomers. The E-isomer is known as geranial or citral A...
, the corresponding aldehyde - NerolNerolNerol is a monoterpene 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 is considered to be fresher.Isomeric with nerol is geraniol,...
, the double bond isomer - RhodinolRhodinolRhodinol is a monoterpene alcohol that occurs naturally in geranium and citronella oils. It is used in cosmetics and perfumery to impart flowery odors....
, a related terpene alcohol - Geranyl pyrophosphateGeranyl pyrophosphateGeranyl pyrophosphate is an intermediate in the HMG-CoA reductase pathway used by organisms in the biosynthesis of farnesyl pyrophosphate, geranylgeranyl pyrophosphate, cholesterol, terpenes and terpenoids....
- Geranylgeranyl pyrophosphateGeranylgeranyl pyrophosphateGeranylgeranyl pyrophosphate is an intermediate in the HMG-CoA reductase pathway used by organisms in the biosynthesis of terpenes and terpenoids. In plants it is also the precursor to carotenoids, gibberellins, tocopherols, and chlorophylls....