Terpineol is any of four isomeric

monoterpenoid Monoterpenes are a class of terpenes that consist of two isoprene units and have the molecular formula C10H16. Monoterpenes may be linear (acyclic) or contain rings (monocyclic and bicyclic). Modified terpenes, such as those containing oxygen funct ...

s. Terpenoids are terpene that are modified by the addition of a

functional group In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the re ...

, in this case, an alcohol. Terpineols have been isolated from a variety of sources such as

cardamom Cardamom (), sometimes cardamon or cardamum, is a spice made from the seeds of several plants in the genera ''Elettaria'' and ''Amomum'' in the family Zingiberaceae. Both genera are native to the Indian subcontinent and Indonesia. They are r ...

, cajuput oil,

pine oil Pine oil is an essential oil obtained from a variety of species of pine, particularly ''Pinus sylvestris''. Typically, parts of the trees that are not used for lumber - stumps, etc. - are ground and subjected to steam distillation. As of 1995, ...

, and

petitgrain Petitgrain () is an essential oil that is extracted from the leaves and green twigs of the bitter orange tree (''Citrus aurantium'' ssp. ''amara'') via steam distillation. It is also known as petitgrain bigarade. Etymology Petitgrain (Fr.: � ...

oil. Four isomers exist: α-, β-, γ-terpineol, and

terpinen-4-ol Terpinen-4-ol is an isomer of terpineol with the chemical formula C10H18O. A primary constituent of tea tree oil, it is obtained as an extract from the leaves, branches, and bark of ''Melaleuca alternifolia'' Cheel. Despite considerable basic and ...

. β- and γ-terpineol differ only by the location of the

double bond In chemistry, a double bond is a covalent bond between two atoms involving four bonding electrons as opposed to two in a single bond. Double bonds occur most commonly between two carbon atoms, for example in alkenes. Many double bonds exist betwee ...

. 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 An odor (American English) or odour ( Commonwealth English; see spelling differences) is caused by one or more volatilized chemical compounds that are generally found in low concentrations that humans and animals can perceive via their se ...

constituents of

lapsang souchong Lapsang souchong (; ) or Zhengshan xiaozhong () is a black tea consisting of leaves that are smoke-dried over a pinewood fire. This smoking is accomplished either as a cold smoke of the raw leaves as they are processed or as a hot smoke of pr ...

tea; the α-terpineol originates in the pine smoke used to dry the tea. (+)-α-terpineol is a chemical constituent of

skullcap Skullcap or skull cap usually refers to various types of headgear. Specifically it may refer to: Headwear * Beanie (seamed cap) * Biretta, forming part of some clerical, academic or legal dress * Calotte (Belgium), a skullcap worn by students at ...

Synthesis and biosynthesis

Although it is naturally occurring, terpineol is commonly manufactured from

alpha-pinene α-Pinene is an organic compound of the terpene class, one of two isomers of pinene. It is an alkene and it contains a reactive four-membered ring. It is found in the oils of many species of many coniferous trees, notably the pine. It is also ...

, which is hydrated in the presence of sulfuric acid. An alternative route starts from

limonene Limonene is a colorless liquid aliphatic hydrocarbon classified as a cyclic monoterpene, and is the major component in the oil of citrus fruit peels. The -isomer, occurring more commonly in nature as the fragrance of oranges, is a flavoring a ...

: : Limonene reacts with

trifluoroacetic acid Trifluoroacetic acid (TFA) is an organofluorine compound with the chemical formula CF3CO2H. It is a structural analogue of acetic acid with all three of the acetyl group's hydrogen atoms replaced by fluorine atoms and is a colorless liquid with ...

in a

Markovnikov addition In organic chemistry, Markovnikov's rule or Markownikoff's rule describes the outcome of some addition reactions. The rule was formulated by Russian chemist Vladimir Markovnikov in 1870. Explanation The rule states that with the addition of a p ...

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. : TerpeneVterpenoid

References

External links

MSDS for alpha-terpineol
* {{Authority control Flavors Monoterpenes Alkenols Cyclohexenes