Geraniol

Geraniol is a monoterpenoid and an alcohol. It is the primary component of citronella oil and is a primary component of rose oil, 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.

Not to be confused with Geranial.
Geraniol[1]
Geraniol
Names
Preferred IUPAC name
(2E)-3,7-Dimethylocta-2,6-dien-1-ol
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.003.071
EC Number
  • 203-377-1
KEGG
UNII
  • InChI=1S/C10H18O/c1-9(2)5-4-6-10(3)7-8-11/h5,7,11H,4,6,8H2,1-3H3/b10-7+ checkY
    Key: GLZPCOQZEFWAFX-JXMROGBWSA-N checkY
  • InChI=1/C10H18O/c1-9(2)5-4-6-10(3)7-8-11/h5,7,11H,4,6,8H2,1-3H3/b10-7+
    Key: GLZPCOQZEFWAFX-JXMROGBWBZ
  • CC(=CCC/C(=C/CO)/C)C
Properties
C10H18O
Molar mass 154.253 g·mol−1
Density 0.889 g/cm3
Melting point −15 °C (5 °F; 258 K)[2]
Boiling point 230 °C (446 °F; 503 K)[2]
686 mg/L (20 °C)[2]
log P 3.28[3]
Hazards
NFPA 704 (fire diamond)
NFPA 704 four-colored diamond
2
1
0
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)
Infobox references

Uses and occurrence

In addition to 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, it is commonly used in perfumes. It is used in flavors 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.[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]

Geranyl pyrophosphate is important in biosynthesis of other terpenes such as myrcene and ocimene.[8] It is also used in the biosynthesis pathway of many cannabinoids in the form of CBGA.[9]

Reactions

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]

Health and safety

Geraniol is classified as D2B (Toxic materials causing other effects) using the Workplace Hazardous Materials Information System (WHMIS).[14]

History

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]

See also

References
  1. "Geraniol". The Merck Index (12th ed.).
  2. Record in the GESTIS Substance Database of the Institute for Occupational Safety and Health
  3. "Geraniol_msds".
  4. "GERANIOL - Cameo Chemicals - NOAA". Retrieved 26 June 2021.
  5. Danka, R. G.; Williams, J. L.; Rinderer, T. E. (1990). "A bait station for survey and detection of honey bees" (PDF). Apidologie. 21 (4): 287–292. doi:10.1051/apido:19900403.
  6. Müller, Günter C.; Junnila, Amy; Kravchenko, Vasiliy D.; Revay, Edita E.; Butler, Jerry; Orlova, Olga B.; Weiss, Robert W.; Schlein, Yosef (March 2008). "Ability of essential oil candles to repel biting insects in high and low biting pressure environments". Journal of the American Mosquito Control Association. 24 (1): 154–160. doi:10.2987/8756-971X(2008)24[154:AOEOCT]2.0.CO;2. ISSN 8756-971X. PMID 18437832. S2CID 41927381.
  7. Holcombe, Luke (9 January 2018) "Wine faults", p. 11.
  8. Eggersdorfer, M. "Terpenes". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a26_205.
  9. Fellermeier M, Zenk MH (May 1998). "Prenylation of olivetolate by a hemp transferase yields cannabigerolic acid, the precursor of tetrahydrocannabinol". FEBS Letters. 427 (2): 283–85. doi:10.1016/S0014-5793(98)00450-5. PMID 9607329.
  10. Stork, Gilbert; Grieco, Paul A.; Gregson, Michael (1974). "Allylic Chlorides from Allylic Alcohols: Geranyl Chloride". Organic Syntheses. 54: 68. doi:10.15227/orgsyn.054.0068.
  11. Jose G. Calzada and John Hooz (1974). "Geranyl chloride". Organic Syntheses. 54: 63. doi:10.15227/orgsyn.054.0063.
  12. Takaya, Hidemasa; Ohta, Tetsuo; Inoue, Shin-ichi; Tokunaga, Makoto; Kitamura, Masato; Noyori, Ryoji (1995). "Asymmetric Hydrogenation of Allylic Alcohols Using BINAP–Ruthenium Complexes: (S)-(−)-citronellol". Organic Syntheses. 72: 74. doi:10.15227/orgsyn.072.0074.; Collective Volume, vol. 9, p. 169
  13. Piancatelli, Giovanni; Leonelli, Francesca (2006). "Oxidation of Nerol to Neral With Iodosobenzene and TEMPO". Organic Syntheses. 83: 18. doi:10.15227/orgsyn.083.0018.
  14. "MSDS – Geraniol". Sigma-Aldrich. Retrieved Feb 15, 2022.
  15. 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 … )
  16. 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.
  17. (Semmler, 1906), p. 491.
  18. 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.
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