Geraniol is a monoterpenoid and an alcohol. It is the primary component of citronella oil and is a primary component of rose oil 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
rose oil,
palmarosa oil, and
citronella oil, it also occurs in small quantities in
Pelargonium,
lemon, and many other
. With a
rose-like scent,
it is commonly used in
and in scents such as
peach,
raspberry,
grapefruit,
apple,
plum, lime, orange,
lemon,
watermelon,
pineapple, and
blueberry.
Geraniol is produced by the scent glands of to mark nectar-bearing flowers and locate the entrances to their hives.
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.[Holcombe, Luke (9 January 2018) "Wine faults" , p. 11.]
Geranyl pyrophosphate is important in biosynthesis of other such as myrcene and ocimene.
Geraniol is used in medicine and food industry
Reactions
In
acidic solutions, geraniol is converted to the cyclic terpene
terpineol. 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
Citral.
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 (WHMIS).
History
Geraniol was first isolated in pure form in 1871 by the German chemist
Oscar Jacobsen (1840–1889).
[ Jacobsen named geraniol on p. 234: "Danach ist dieser Körper, das Geraniol, isomer mit dem Borneol … " (Accordingly this body i.e.,, geraniol, is isomeric with borneol … )][ From p. 292: "Von dem Geraniol ist zu erwähnen, daß … erst Jacobsen (A. 157, 232) brachte im Jahre 1870 über den Alkohol, den er Geraniol nannte, nähere Angaben, er stellte die Formel C10H18O auf, ohne weitere Konstitionsangaben zu machen." (It should be mentioned about geraniol that … Jacobsen (A. 157, 232) first gathered in 1870 more detailed data about the alcohol, which he named geraniol ; he established its empirical formula C10H18O, without providing further data about its chemical structure.) See also: § 49. Geraniol C10H18O, pp. 439-493. On p. 439, two hypothetical structures of geraniol are proposed.] Using
distillation, Jacobsen obtained geraniol from an essential oil produced in India which was obtained from the so-called
geranium grass.
[(Semmler, 1906), p. 491.] This essence, after which the compound was named, was a 50% cheaper substitute for the essence of the proper
geranium 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.]
See also
External links
