Geraniol

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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 occurrenceEdit

In addition to being found in rose oil, palmarosa oil, and citronella oil, it also occurs in small quantities in geranium, lemon, and many other essential oils. With a rose-like scent,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> it is commonly used in perfumes and in scents such as peach, 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.<ref>Template:Cite journal</ref> It is also commonly used as an insect repellent, especially for mosquitoes.<ref>Template:Cite journal</ref>

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.<ref>Holcombe, Luke (9 January 2018) "Wine faults" Template:Webarchive, p. 11.</ref>

Geranyl pyrophosphate is important in biosynthesis of other terpenes such as myrcene and ocimene.<ref name=UllmannEgg>Template:Ullmann</ref> It is also used in the biosynthesis pathway of many cannabinoids in the form of CBGA.<ref name="pmid9607329">Template:Cite journal</ref>

ReactionsEdit

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.<ref>Template:OrgSynth</ref><ref>Template:OrgSynth</ref> It can be oxidized to the aldehyde geranial.<ref>Template:OrgSynth</ref> Hydrogenation of the two C=C bonds over a nickel catalyst gives tetrahydrogeraniol.<ref>Template:OrgSynth</ref><ref>Template:Cite book</ref>

Health and safetyEdit

Geraniol is classified as D2B (Toxic materials causing other effects) using the Workplace Hazardous Materials Information System (WHMIS).<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

HistoryEdit

Geraniol was first isolated in pure form in 1871 by the German chemist Oscar Jacobsen (1840–1889).<ref>Template:Cite journal 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 … )</ref><ref>Template:Cite book 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.</ref> Using distillation, Jacobsen obtained geraniol from an essential oil produced in India which was obtained from the so-called geranium grass.<ref>(Semmler, 1906), p. 491.</ref> 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.<ref>Template:Cite book</ref>

The chemical structure of geraniol was determined in 1919 by the French chemist Albert Verley (1867–1959).<ref>Template:Cite journal The chemical structure of geraniol appears on p. 70.</ref>

ReferencesEdit

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External linksEdit

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