Terpineol is any of four

isomer In chemistry, isomers are molecules or polyatomic ions with identical molecular formula – that is, the same number of atoms of each element (chemistry), element – but distinct arrangements of atoms in space. ''Isomerism'' refers to the exi ...

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 any substituent or moiety (chemistry), moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions r ...

, in this case, an

alcohol Alcohol may refer to: Common uses * Alcohol (chemistry), a class of compounds * Ethanol, one of several alcohols, commonly known as alcohol in everyday life ** Alcohol (drug), intoxicant found in alcoholic beverages ** Alcoholic beverage, an alco ...

. 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 genus (biology), genera ''Elettaria'' and ''Amomum'' in the family Zingiberaceae. Both genera are native to the Indian subcontinent and Indon ...

, 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, sy ...

, 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

s exist: α-terpineol, β-terpineol, 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-Terpineol 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 betw ...

. 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 a smell or a scent caused by one or more volatilized chemical compounds generally found in low concentrations that humans and many animals can perceive v ...

constituents of

lapsang souchong Lapsang souchong (; ) or Zhengshan xiaozhong (, 'Proper Mountain Small Varietal') 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 ...

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

Synthesis and biosynthesis

Although it is naturally occurring, terpineol is commonly manufactured from alpha-pinene, 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 essential oil of citrus fruit peels. The (+)-isomer, occurring more commonly in nature as the fragrance of oranges, ...

: : Limonene reacts with

trifluoroacetic acid Trifluoroacetic acid (TFA) is a synthetic organofluorine compound with the chemical formula CF3CO2H. It belongs to the subclass of per- and polyfluoroalkyl substances (PFASs) known as ultrashort-chain perfluoroalkyl acids (PFAAs). TFA is not ...

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 ...

to a trifluoroacetate intermediate, which is easily hydrolyzed with

sodium hydroxide Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula . It is a white solid ionic compound consisting of sodium cations and hydroxide anions . Sodium hydroxide is a highly corrosive base (chemistry), ...

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