Borneol is a

bicyclic In chemistry, a bicyclic molecule () is a molecule that features two joined rings. Bicyclic structures occur widely, for example in many biologically important molecules like α-thujene and camphor. A bicyclic compound can be carbocyclic (all ...

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. T ...

and a

terpene Terpenes () are a class of natural products consisting of compounds with the formula (C5H8)n for n > 1. Comprising more than 30,000 compounds, these unsaturated hydrocarbons are produced predominantly by plants, particularly conifers. Terpenes ...

derivative. The

hydroxyl In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydro ...

group in this compound is placed in an '' endo'' position. The exo diastereomer is called

isoborneol Isoborneol is a bicyclic organic compound and a terpene derivative. The hydroxyl group in this compound is placed in an ''exo'' position. The endo diastereomer is called borneol. Being chiral, isoborneol exists as enantiomers. Preparation Isob ...

. Being chiral, borneol exists as enantiomers, both of which are found in nature.

Reactions

Borneol is

oxidized Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a ...

to the ketone ( camphor).

Occurrence

The compound was named in 1842 by the French chemist Charles Frédéric Gerhardt. Borneol can be found in several species of ''

Heterotheca ''Heterotheca'', (common names goldenasters, camphorweed, or telegraph weed) are North American plants in the family Asteraceae. Etymology ''Heterotheca'' comes from Ancient Greek "other, different" and "case, chest", and refers to the fact ...

'', '' Artemisia'', ''Rosmarinus officinalis'' (

rosemary ''Salvia rosmarinus'' (), commonly known as rosemary, is a shrub with fragrant, evergreen, needle-like leaves and white, pink, purple, or blue flowers, native to the Mediterranean region. Until 2017, it was known by the scientific name ''Rosmar ...

) '' Dipterocarpaceae'', ''

Blumea balsamifera ''Blumea balsamifera'' is a flowering plant belonging to the genus ''Blumea'' of the family Asteraceae. It is also known as Ngai camphor and sambong (also sembung). Description In the Philippines, where it is most commonly known as sambong, ''B ...

'' and '' Kaempferia galanga''. It is one of the chemical compounds found in

castoreum Castoreum is a yellowish exudate from the castor sacs of mature beavers. Beavers use castoreum in combination with urine to scent mark their territory. Both beaver sexes have a pair of castor sacs and a pair of anal glands, located in two cavitie ...

. This compound is gathered from the beaver's plant food.

Synthesis

Borneol can be synthesized by reduction of camphor by the

Meerwein–Ponndorf–Verley reduction The Meerwein–Ponndorf–Verley (MPV) reduction in organic chemistry is the reduction of ketones and aldehydes to their corresponding alcohols utilizing aluminium alkoxide catalysis in the presence of a sacrificial alcohol. The advantages of th ...

(a reversible process). Reduction of camphor with

sodium borohydride Sodium borohydride, also known as sodium tetrahydridoborate and sodium tetrahydroborate, is an inorganic compound with the formula Na BH4. This white solid, usually encountered as an aqueous basic solution, is a reducing agent that finds applica ...

(fast and irreversible) gives instead the

diastereomer In stereochemistry, diastereomers (sometimes called diastereoisomers) are a type of stereoisomer. Diastereomers are defined as non-mirror image, non-identical stereoisomers. Hence, they occur when two or more stereoisomers of a compound have di ...

. :

Uses

Whereas ''d''-borneol was the enantiomer that used to be the most readily available commercially, the more commercially available enantiomer now is ''l''-borneol, which also occurs in nature. Borneol from ''

Dipterocarpus '' D. retusus'' in Köhler ''Dipterocarpus'' is a genus of flowering plants and the type genus of family Dipterocarpaceae. ''Dipterocarpus'' is the third-largest and most diverse genus among the Dipterocarpaceae. The species are well known for ...

'' spp. is used in traditional Chinese medicine. An early description is found in the Bencao Gangmu. Borneol is a component of many essential oils and it is a natural insect repellent. It also generates a TRPM8-mediated cooling sensation similar to menthol. Laevo-borneol is used in perfumery. It has a balsamic odour type with pine, woody and camphoraceous facets.

Toxicology

Borneol may cause eye, skin, and respiratory irritation; it is harmful if swallowed. Acute exposure may cause headache, nausea, vomiting, dizziness, lightheadedness, and syncope. Exposure to higher levels or over a longer period of time may cause restlessness, difficulty concentrating, irritability, and seizures.HAZARDOUS SUBSTANCE FACT SHEET
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Skin Irritation

Borneol has been shown to have little to no irritation effect when applied to the human skin at doses used in fine fragrance formulation. Skin exposure can lead to sensitization and a future allergic contact dermatitis, allergic reaction even to small quantities.

Derivatives

The bornyl group is a univalent radical C₁₀H₁₇ derived from borneol by removal of hydroxyl and is also known as 2-bornyl. Isobornyl is the univalent radical C₁₀H₁₇ that is derived from isoborneol. The structural isomer fenchol is also a widely used compound derived from certain essential oils. Bornyl acetate is the acetate ester of borneol.

Notes and references

External links

NIST datasheet including full spectroscopic data

{{GABAAR PAMs Secondary alcohols Monoterpenes GABAA receptor positive allosteric modulators Bicyclic compounds Cyclopentanes