alpha-terpineol
Verifiedfieldschanged
Watchedfieldschanged
Verifiedrevid470602595
Iupacnamesp-Menth-1-en-8-ol
2-(4-Methylcyclohex-3-en-1-yl)propan-2-ol
Othernames
  • 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

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.[1] 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.

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.[2] (+)-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".[3] Whilst both enantiomers of α-terpineol exhibit a floral lilac aroma,[4][5] the laevo form (−)-α-terpineol, is reportedly more terpenic. The aroma of β-terpineol is described as "pungent, earthy, woody".[6]. The aroma of γ-terpineol is "pine, floral, lilac".[7] 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".[8]

Synthesis and biosynthesis

Although it is naturally occurring, terpineol is commonly manufactured from alpha-pinene, which is hydrated in the presence of sulfuric acid.[9]

An alternative route starts from limonene:[10]

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.

References

  1. ^
  2. ^ Yao, Shan-Shan; Guo, Wen-Fei; Lu, Yi; Jiang, Yuan-Xun (2005). "Flavor Characteristics of Lapsang Souchong and Smoked Lapsang Souchong, a Special Chinese Black Tea with Pine Smoking Process". Journal of Agricultural and Food Chemistry. 53 (22): 8688–93. Bibcode:2005JAFC...53.8688Y. doi:10.1021/jf058059i. PMID 16248572
  3. ^ "alpha-terpineol". Scents and Flavors. Scents and Flavors. Retrieved 5 April 2026.
  4. ^ "(+)-alpha-terpineol". Scents and Flavors. Scents and Flavors. Retrieved 5 April 2026.
  5. ^ "(−)-alpha-terpineol". Scents and Flavors. Scents and Flavors. Retrieved 5 April 2026.
  6. ^ "beta-terpineol". Scents and Flavors. Scents and Flavors. Retrieved 5 April 2026.
  7. ^ "gamma-terpineol". Scents and Flavors. Scents and Flavors. Retrieved 5 April 2026.
  8. ^ "4-carvomenthenol". Scents and Flavors. Scents and Flavors. Retrieved 5 April 2026.
  9. ^
  10. ^ Yuasa, Yoshifumi & Yuasa, Yoko (2006). "A Practical Synthesis of d-α-Terpineol via Markovnikov Addition of d-Limonene Using Trifluoroacetic Acid". Organic Process Research & Development. 10 (6): 1231–1232. doi:10.1021/op068012d