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. The
functional group derived from geraniol (in essence, geraniol lacking the terminal
−OH) is called geranyl.
Geraniol is produced by the
scent glands of
honeybees to mark nectar-bearing flowers and locate the entrances to their hives.[5] It is also commonly used as an insect repellent, especially for mosquitoes.[6]
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.[7]
In
acidic solutions, geraniol is converted to the cyclic terpene
α-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.[10][11] It can be hydrogenated.[12] It can be oxidized to the aldehyde
geranial.[13]
Geraniol was first isolated in pure form in 1871 by the German chemist
Oscar Jacobsen (1840–1889).[15][16] Using
distillation, Jacobsen obtained geraniol from an essential oil which was obtained from geranium grass (Andropogon schoenanthus) and which was produced in India.[17] The chemical structure of geraniol was determined in 1919 by the French chemist Albert Verley (1867–1959).[18]
^Jacobsen, Oscar (1871).
"Untersuchung der indischen Geraniumöls" [InvestIgation of Indian oil from geranium [grass]]. Annalen der Chemie und Pharmacie (in German). 157: 232–239. Jacobsen named geraniol on p. 234: "Danach ist dieser Körper, das Geraniol, isomer mit dem Borneol … " (Accordingly this body [i.e., substance], geraniol, is isomeric with borneol … )
^Semmler, F.W. (1906).
Die ätherischen Öle [The Volatile Oils] (in German). Vol. 1. Leipzig, Germany: Von Veit & Co. p. 292. 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.
^Verley, Albert (1919).
"Sur la constitution du géraniol, du linalool et du nérol" [On the chemical structure of geraniol, linalool, and nerol]. Bulletin de la Société Chimique de France. 4th series (in French). 25: 68–80. The chemical structure of geraniol appears on p. 70.