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.[2] Four isomers exist: α-, β-, γ-terpineol, and terpinen-4-ol. β- 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.
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| Names | |||
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| IUPAC names
p-Menth-1-en-8-ol | |||
| Other names
2-(4-Methyl-1-cyclohex-3-enyl)propan-2-ol | |||
| Identifiers | |||
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3D model (JSmol) |
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| 2325137 | |||
| ChEBI |
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PubChem CID |
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CompTox Dashboard (EPA) |
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| Properties | |||
| C10H18O | |||
| Molar mass | 154.253 g·mol−1 | ||
| Appearance | Colorless liquid[1] | ||
| Density | 0.93 g/cm3[1] | ||
| Melting point | −35.9 to −28.2 °C (−32.6 to −18.8 °F; 237.2 to 245.0 K)[1] (mixture of isomers) | ||
| Boiling point | 214–217 °C (417–423 °F; 487–490 K)[1] (mixture of isomers) | ||
| 2.42 g/L[1] | |||
| −111.9·10−6 cm3/mol | |||
| Hazards | |||
| NFPA 704 (fire diamond) | |||
| Flash point | 88 °C (190 °F; 361 K)[1] | ||
| Safety data sheet (SDS) | External MSDS | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |||
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.[3] (+)-α-terpineol is a chemical constituent of skullcap.
Although it is naturally occurring, terpineol is commonly manufactured from alpha-pinene, which is hydrated in the presence of sulfuric acid.[4]
An alternative route starts from limonene:[5]
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.
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Media related to Terpineols at Wikimedia Commons