{{chembox | Verifiedfields = changed | Watchedfields = changed | verifiedrevid = 470602595 | Name = alpha-terpineol | ImageFileL1 = Terpineol alpha.svg | ImageNameL1 = Skeletal formula | ImageFileR1 = Alpha-terpineol-3D-balls.png | ImageNameR1 = Ball-and-stick model | ImageName = alpha-Terpineol | IUPACNames = ''p''-Menth-1-en-8-ol<br>2-(4-Methylcyclohex-3-en-1-yl)propan-2-ol | OtherNames = {{Unbulleted list|2-(4-Methyl-1-cyclohex-3-enyl)propan-2-ol|alpha-Terpineol|α-Terpineol|α,α,4-Trimethylcyclohex-3-ene-1-methanol|Terpene alcohol|Terpineol AP}} | Section1 = {{Chembox Identifiers | index_label = α | index1_label = β | index2_label = γ | index3_label = 4- | CASNo_Ref = {{cascite|correct|CAS}} | CASNo = 98-55-5 | CASNo1 = 138-87-4 | CASNo2 = 586-81-2 | CASNo3 = 562-74-3 | ChEBI_Ref = {{ebicite|correct|EBI}} | ChEBI = 22469 | ChEBI1 = 132899 | ChEBI2 = 81151 | ChEBI3 = 78884 | Beilstein = 2325137 | ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} | ChemSpiderID = 13850142 | ChemSpiderID1 = 8418 | ChemSpiderID2 = 10983 | ChemSpiderID3 = 10756 | ChEMBL_Ref = {{ebicite|changed|EBI}} | ChEMBL = 507795 | ChEMBL3 = 507795 | DTXSID3 = DTXSID4044824 | EC_number = 202-680-6 | EC_number1 =205-342-6 | EC_number2 = 209-584-3 | EC_number3 = 209-235-5 | KEGG1 = C17517 | KEGG3 = C17073 | PubChem = 17100 | PubChem1 = 8748 | PubChem2 = 11467 | PubChem3 = 11230 | UNII_Ref = {{fdacite|correct|FDA}} | UNII = 21334LVV8W | UNII2 = 5PH9U7XEWS | InChI = 1/C10H18O/c1-8-4-6-9(7-5-8)10(2,3)11/h4,9,11H,5-7H2,1-3H3 | InChIKey = WUOACPNHFRMFPN-UHFFFAOYAL | StdInChI_Ref = {{stdinchicite|correct|chemspider}} | StdInChI = 1S/C10H18O/c1-8-4-6-9(7-5-8)10(2,3)11/h4,9,11H,5-7H2,1-3H3 | StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} | StdInChIKey = WUOACPNHFRMFPN-UHFFFAOYSA-N | SMILES = C\C1=C\CC(CC1)C(O)(C)C }} | Section2 = {{Chembox Properties | C=10 | H=18 | O=1 | Density = 0.93{{nbsp}}g/cm<sup>3</sup><ref name=GESTIS/> | MeltingPtC = -35.9 to -28.2 | MeltingPt_notes = (mixture of isomers) | MeltingPt_ref = <ref name=GESTIS>{{GESTIS|ZVG=122876}}</ref> | BoilingPtC = 214–217 | BoilingPt_notes = (mixture of isomers) | BoilingPt_ref = <ref name=GESTIS/> | Solubility = 2.42{{nbsp}}g/L<ref name=GESTIS/> | Appearance = Colorless liquid<ref name=GESTIS/> |Odor = Pleasant, lilac-like | MagSus = {{val|-111.9e-6|u=cm<sup>3</sup>/mol}} }} | Section3 = {{Chembox Hazards | ExternalSDS = [http://hazard.com/msds/mf/baker/baker/files/t0364.htm External MSDS] | NFPA-H = 2 | NFPA-F = 1 | NFPA-R = 0 | NFPA-S = | HPhrases = | PPhrases = | GHS_ref = | FlashPtC = 88 | FlashPt_ref = <ref name=GESTIS/> }} }}
'''Terpineol''' is any of four isomeric monoterpenoids. Terpenoids are terpene that are modified by the addition of a functional group, in this case, an alcohol. Terpineols have been isolated from a variety of sources such as cardamom, cajuput oil, pine oil, and petitgrain oil.<ref>{{Merck11th|page=9103}}</ref> Four isomers exist: α-terpineol, β-terpineol, γ-terpineol, and terpinen-4-ol. β-Terpineol and γ-terpineol differ only by the location of the double bond. Terpineol is usually a mixture of these isomers with α-terpineol as the major constituent.
:left|thumb|350x350px|Terpineols: alpha-, beta-, gamma-, and the 4-terpineol isomer{{clear left}}
Terpineol has a pleasant odor similar to lilac and is a common ingredient in perfumes, cosmetics, and flavors. α-Terpineol is one of the two most abundant aroma constituents of lapsang souchong tea; the α-terpineol originates in the pine smoke used to dry the tea.<ref>{{cite journal|first1=Shan-Shan |last1=Yao |first2=Wen-Fei |last2=Guo |first3=Yi |last3=Lu |first4=Yuan-Xun |last4=Jiang |year=2005 |title=Flavor Characteristics of Lapsang Souchong and Smoked Lapsang Souchong, a Special Chinese Black Tea with Pine Smoking Process |journal=Journal of Agricultural and Food Chemistry |volume=53 |issue=22 |url=http://d.wanfangdata.com.cn/NSTLQK_NSTL_QK10615205.aspx | doi = 10.1021/jf058059i |pmid=16248572 |pages=8688–93|bibcode=2005JAFC...53.8688Y |url-access=subscription }}</ref> (+)-α-Terpineol is a chemical constituent of skullcap.
α-Terpineol has an aroma described as "pine, terpenic, lilac, citrus, woody, floral, resinous, cooling, lemon, lime".<ref>{{cite web |title=alpha-terpineol|url=https://scentsandflavors.com/database/9dbb5015-fa2b-41f8-b35a-ca01a4d81ef8|website=Scents and Flavors |publisher=Scents and Flavors |access-date=5 April 2026}}</ref> Whilst both enantiomers of α-terpineol exhibit a floral lilac aroma,<ref>{{cite web |title=(+)-alpha-terpineol|url=https://scentsandflavors.com/database/9dbb56dc-3c69-4941-9c60-5b2e9104c16c|website=Scents and Flavors |publisher=Scents and Flavors |access-date=5 April 2026}}</ref><ref>{{cite web |title=(−)-alpha-terpineol|url=https://scentsandflavors.com/database/9dbb5385-fca8-44da-a482-7b657f14d108|website=Scents and Flavors |publisher=Scents and Flavors |access-date=5 April 2026}}</ref> the laevo form (−)-α-terpineol, is reportedly more terpenic. The aroma of β-terpineol is described as "pungent, earthy, woody".<ref>{{cite web |title=beta-terpineol|url=https://scentsandflavors.com/database/9dbb511e-74cd-4aed-bc09-6c723bb99a01|website=Scents and Flavors |publisher=Scents and Flavors |access-date=5 April 2026}}</ref>. The aroma of γ-terpineol is "pine, floral, lilac".<ref>{{cite web |title=gamma-terpineol|url=https://scentsandflavors.com/database/9dbb51e7-21f2-46d9-ad96-5d1381b4e383|website=Scents and Flavors |publisher=Scents and Flavors |access-date=5 April 2026}}</ref> The aroma of 4-terpinenol (also known as terpinen-4-ol or 4-carvomenthenol), is described as "peppery, woody, earthy, musty, sweet, mentholic, citrus, terpenic, spicy".<ref>{{cite web |title=4-carvomenthenol|url=https://scentsandflavors.com/database/9dbb50aa-eb18-4874-bde4-3a99de690275|website=Scents and Flavors |publisher=Scents and Flavors |access-date= 5 April 2026}}</ref>
==Synthesis and biosynthesis== Although it is naturally occurring, terpineol is commonly manufactured from alpha-pinene, which is hydrated in the presence of sulfuric acid.<ref name=Ull>{{Ullmann|title= Turpentines, 16. Pine Oil |first1= Manfred |last1= Gscheidmeier |first2= Helmut |last2= Fleig |date= June 15, 2000 |doi=10.1002/14356007.a27_267|isbn = 978-3527306732}}</ref>
An alternative route starts from limonene:<ref>{{cite journal | doi = 10.1021/op068012d | title = A Practical Synthesis of ''d''-α-Terpineol via Markovnikov Addition of ''d''-Limonene Using Trifluoroacetic Acid | year = 2006 | last1 = Yuasa | first1 = Yoshifumi | last2 = Yuasa | first2 = Yoko | journal = Organic Process Research & Development | volume = 10 | issue = 6 | pages = 1231–1232}}</ref>
:thumb|left|400px|Terpineol synthesis from limonene{{clear left}}
Limonene reacts with trifluoroacetic acid in a Markovnikov addition to a trifluoroacetate intermediate, which is easily hydrolyzed with sodium hydroxide to α-terpineol with 7% selectivity. Side-products are β-terpineol in a mixture of the ''cis'' isomer, the ''trans'' isomer, and 4-terpineol.
The biosynthesis of α-terpineol proceeds from geranyl pyrophosphate, which releases pyrophosphate to give the '''terpinyl cation'''. This carbocation is the precursor to many terpenes and terpenoids. Its hydrolysis gives terpineol. :[[File:TerpeneVterpenoid.svg|thumb|460px|left|Biosynthetic conversion of geranyl pyrophosphate to the terpenes α-pinene and β-pinene (right) and to α-terpineol (bottom left).<ref name=Crot>{{cite book|chapter=Cyclization enzymes in the biosynthesis of monoterpenes, sesquiterpenes, and diterpenes|last1=Davis |first1=Edward M. |last2=Croteau |first2=Rodney |title=Biosynthesis|journal=Topics in Current Chemistry|year=2000|volume=209|pages=53–95|doi=10.1007/3-540-48146-X_2|isbn=978-3-540-66573-1}}</ref>]] {{clear left}}
==References== {{reflist}}
==External links== * [http://hazard.com/msds/mf/baker/baker/files/t0364.htm MSDS for alpha-terpineol] * {{commons category-inline}}
{{Authority control}}
Category:Flavors Category:Monoterpenes Category:Alkenols Category:Cyclohexenes