Citronellol: Difference between revisions

{{Use dmy dates|date=March 2021}}

{{Short description|Pair of enantiomers}}

{{distinguish|Citronellal}}

| verifiedrevid = 443528686

| Name = Citronellol

| ImageFile = Citronellol enantiomers.svg

| ImageSize = 250px

| ImageAlt = Skeletal formula of (+)-citronellol and (−)-citronellol

| ImageCaption = (+)-Citronellol (left) and (−)-citronellol (right)

| ImageFile1 = (+)-Citronellol 3D ball.png

| ImageAlt1 = Ball-and-stick model of the (+)-citronellol molecule

| ImageCaption1 = ''R''-(+)-Citronellol

| ImageFile2 = (-)-Citronellol 3D ball.png

| ImageAlt2 = Ball-and-stick model of the (−)-citronellol molecule

| ImageCaption2 = ''S''-(−)-Citronellol

| IUPACName = 3,7-Dimethyloct-6-en-1-ol

| OtherNames = (±)-β-Citronellol; Cephrol, Corol

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| UNII = 565OK72VNF

| UNII1_Ref = {{fdacite|correct|FDA}}

| UNII1 = P01OUT964K

| UNII1_Comment = (''R'')

| UNII2_Ref = {{fdacite|correct|FDA}}

| UNII2 = 8RSY5Y5658

| UNII2_Comment = (''S'')

| KEGG_Ref = {{keggcite|correct|kegg}}

| CASNo1_Ref = {{cascite|correct|CAS}}

| CASNo1 = 1117-61-9

| CASNo1_Comment =(''R'')

| CASNo2_Ref = {{cascite|correct|CAS}}

| CASNo2 = 7540-51-4

| CASNo2_Comment =(''S'')

| ChEBI_Ref = {{ebicite|correct|EBI}}

| PubChem = 8842

| EC_number = 247-737-6

| Beilstein = 1362474

| C=10|H=20|O=1

| Density = 0.855 g/cm³

| BoilingPtC = 225

| Viscosity = 11.1 mPa s

}}

| Section3 = {{Chembox Hazards

| NFPA-H = 1

| NFPA-F = 2

| NFPA-R = 0

| GHSPictograms = {{GHS07}}{{GHS09}}

| GHSSignalWord = Warning

| HPhrases = {{H-phrases|315|317|319}}

| PPhrases = {{P-phrases|261|264|272|273|280|302+352|305+351+338|321|332+313|333+313|337+313|362|363|391|501}}

}}

'''Citronellol''', or dihydrogeraniol, is a natural acyclic mono[[terpenoid]]. Both [[enantiomer]]s occur in nature. (+)-Citronellol, which is found in [[citronella oil]]s, including ''[[Cymbopogon nardus]]'' (50%), is the more common isomer. (−)-Citronellol is widespread, but particularly abundant in the oils of [[rose]] (18–55%) and ''[[Pelargonium]]'' geraniums.<ref>{{cite book | last= Lawless |first=J. | title = The Illustrated Encyclopedia of Essential Oils | isbn = 978-1-85230-661-8| year = 1995 }}</ref>

==Preparation==

Several million kilograms of citronellol are produced annually. It is mainly obtained by [[hydrogenation]] of [[geraniol]] or [[nerol]] over [[copper chromite]] catalyst.<ref name=KO>{{cite book |doi=10.1002/0471238961.2005181602120504.a01.pub2|chapter=Terpenoids |title=Kirk-Othmer Encyclopedia of Chemical Technology |year=2006 |last1=Sell |first1=Charles S. |isbn=0471238961 }}</ref> [[Homogeneous catalysis|Homogeneous catalysts]] are used for the production of [[enantiomer]]s.<ref>{{cite book | first= Robert H. |last=Morris | chapter = Ruthenium and Osmium | title = The Handbook of Homogeneous Hydrogenation | editor1-first = J. G. |editor1-last=De Vries |editor2-first= C. J. |editor2-last=Elsevier | year = 2007 | publisher = Wiley-VCH | location = Weinheim | isbn = 978-3-527-31161-3}}</ref><ref>{{Cite journal | doi = 10.1016/0957-4166(95)00015-H | title = Catalytic Synthesis of (''R'')- and (''S'')-citronellol by homogeneous hydrogenation over amidophosphinephosphinite and diaminodiphosphine rhodium complexes | year = 1995 | last1 = Ait Ali | first1 = M. | last2 = Allaoud | first2 = S. | last3 = Karim | first3 = A. | last4 = Roucoux | first4 = A. | last5 = Mortreux | first5 = A. | journal = Tetrahedron: Asymmetry | volume = 6 | issue = 2 | pages = 369}}</ref>

==Uses==

Citronellol is used in perfumes and as a fragrance in cleaning products. In many applications, one of the enantiomers is preferred. It is a component of citronella oil, an insect repellant.<ref name=KO/>

Citronellol is used as a raw material for the production of [[rose oxide]].<ref name=KO/><ref>{{cite journal | title="Dark" Singlet Oxygenation of β-Citronellol: A Key Step in the Manufacture of Rose Oxide | journal=Organic Process Research & Development | doi=10.1021/op900076g | volume=14 | year=2010 | pages=259–262 | last1 = Alsters | first1 = Paul L. | last2 = Jary | first2 = Walther | last3 = Aubry | first3 = Jean-Marie}}</ref> It is also a precursor to many commercial and potential fragrances such as citronellol acetate, citronellyl oxyacetaldehyde, citronellyl methyl acetal, and ethyl citronellyl oxalate.<ref name=KO/>

==Health and safety==

The United States FDA considers citronellol as [[generally recognized as safe]] (GRAS) for food use.<ref name = usepa>{{cite web|url=http://www.epa.gov/pesticides/biopesticides/ingredients/factsheets/factsheet_167004.htm|title=Redirect|work=epa.gov|accessdate=29 July 2015}}</ref> Citronellol is subject to restrictions on its use in perfumery,<ref>{{cite web |url=http://www.ifraorg.org/en-us/standards_restricted/s3/p3 |title=Standards Restricted - IFRA International Fragrance Association |accessdate=19 July 2012 |url-status=dead |archiveurl=https://web.archive.org/web/20120106222844/http://www.ifraorg.org/en-us/standards_restricted/s3/p3 |archivedate=6 January 2012 }}</ref> as some people may become sensitised to it, but the degree to which citronellol can cause an allergic reaction in humans is disputed.<ref>{{Cite web |url=http://www.leffingwell.com/Cropwatch%20Claims%20Victory%20Over%2026%20Allergens.pdf |title=Cropwatch Report April 2008 |access-date=19 July 2012 |archive-url=https://web.archive.org/web/20140210163144/http://www.leffingwell.com/Cropwatch%20Claims%20Victory%20Over%2026%20Allergens.pdf |archive-date=10 February 2014 |url-status=dead }}</ref><ref>[http://www2.mst.dk/common/Udgivramme/Frame.asp?pg=http://www2.mst.dk/udgiv/publications/2006/87-7052-278-2/html/kap07_eng.htm Survey and health assessment of chemical substances in massage oils] {{webarchive|url=https://web.archive.org/web/20070927205013/http://www2.mst.dk/common/Udgivramme/Frame.asp?pg=https%3A%2F%2Frp.liu233w.com%3A443%2Fhttp%2Fwww2.mst.dk%2Fudgiv%2Fpublications%2F2006%2F87-7052-278-2%2Fhtml%2Fkap07_eng.htm |date=27 September 2007 }}</ref>

In terms of dermal safety, citronellol has been evaluated as an insect repellent.<ref>{{cite journal | last1= Taylor |first1=W. G. |last2=Schreck |first2=C. E. | title = Chiral-phase capillary gas chromatography and mosquito repellent activity of some oxazolidine derivatives of (+)- and (−)-citronellol | journal = Journal of Pharmaceutical Sciences| year = 1985 | volume = 74 | issue = 5 | pages = 534–539 | doi = 10.1002/jps.2600740508 | pmid = 2862274| url = https://zenodo.org/record/1229253}}</ref> <!--very niche and as a mite attractant.<ref name = usepa>{{cite web|url=http://www.epa.gov/pesticides/biopesticides/ingredients/factsheets/factsheet_167004.htm|title=Redirect|work=epa.gov|accessdate=29 July 2015}}</ref> Citronellol is a good mosquito repellent at short distances, but protection greatly lessens when the subject is slightly further from the source.<ref>{{Cite journal | doi = 10.1016/j.actatropica.2013.03.011 | title = Reduction of mosquito biting-pressure: Spatial repellents or mosquito traps? A field comparison of seven commercially available products in Israel | year = 2013 | last1 = Revay | first1 = Edita E. | last2 = Kline | first2 = Daniel L. | last3 = Xue | first3 = Rui-De | last4 = Qualls | first4 = Whitney A. | last5 = Bernier | first5 = Ulrich R. | last6 = Kravchenko | first6 = Vasiliy D. | last7 = Ghattas | first7 = Nina | last8 = Pstygo | first8 = Irina | last9 = Müller | first9 = Günter C. | journal = Acta Tropica | volume = 127 | pages = 63–68 | pmid = 23545129 | issue = 1}}</ref> When complexed with β-[[cyclodextrin]], it has on average a 90-minute protection duration against mosquitoes.<ref>{{cite journal | doi = 10.1007/s10847-011-9985-7 | title = Investigation of inclusion complexes of citronella oil, citronellal and citronellol with β-cyclodextrin for mosquito repellent | year = 2011 | last1 = Songkro | first1 = Sarunyoo | last2 = Hayook | first2 = Narissara | last3 = Jaisawang | first3 = Jittarat | last4 = Maneenuan | first4 = Duangkhae | last5 = Chuchome | first5 = Thitima | last6 = Kaewnopparat | first6 = Nattha | journal = Journal of Inclusion Phenomena and Macrocyclic Chemistry | volume = 72 | issue = 3–4 | pages = 339| s2cid = 93566912 }}</ref>-->

* ''[[Pelargonium graveolens]]''

* [[Perfume intolerance]] (allergy)

==References==

[[Category:Alkenols]]