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Description
Terpineol is a naturally occurring monoterpene alcohol found in various essential oils, including pine, tea tree, eucalyptus, and other aromatic plants.
Terpineol is commonly encountered as a mixture of isomers, with α-terpineol being one of the most important forms.
Its molecular formula is C₁₀H₁₈O, and its molecular weight is approximately 154.25 g/mol.
CAS No.98-55-5
Chemical Name:alpha-Terpineol
CBNumber:CB6229317
Molecular Formula:C10H18O
Molecular Weight:154.25
MDL Number:MFCD00001557
MOL File:98-55-5.mol
Synonyms: Α-TERPINEOL, A-TERPINEOL, l-α-Terpineol, P-MENTH-1-EN-8-OL, TERPINENOL, 2-(4-Methylcyclohex-3-en-1-yl)propan-2-ol, α-Terpineo, alfa-terpineol, Terpenol, FEMA 3045
Description
(-)-alpha terpineol is the alpha form of terpineol, a naturally monoterpene alcohol that can be isolated from various kinds of sources such as cajuput oil, pine oil, and petitgrain oil.
The alpha form is the major constituent of terpineol.
Terpineol is a common component in perfumes, cosmetic and flavors.
Terpineol is also a kind of solvent used for extracting natural spices and as a kind of solvent of acetate fibers.
Moreover, Terpineol exhibited strong and broad antimicrobial activity against fungi, bacteria and virus.
Study has demonstrated that is antibacterial (bactericidal) effect originated from its destroying effect on the cell wall and cell membrane of bacteria.
Terpineol also has certain anticonvulsant activity.
Terpineol is generally a colorless to pale yellow liquid or crystalline solid, depending on the isomer and temperature.
Terpineol has a characteristic pleasant floral, lilac-like, piney, or citrus-like odor and is only slightly soluble in water but readily soluble in many organic solvents.
General Description
α-Terpineol is a monoterpene alcohol.
It is one of the components responsible for the antifungal activity of Melaleuca alternifolia (tea tree) essential oil.
The reaction rate constant of α-terpineol with OH radical and ozone was found to be (1.9±0.5)×10-10cm3 molecule-1s-1 and (3.0±0.2)×10-16cm3 molecule-1s-1, respectively.
Uses
Terpineol is widely used in several industries:
Fragrance industry: Used as a fragrance ingredient in perfumes, soaps, detergents, and personal-care products.
Flavor industry: Certain terpineol isomers are used as flavoring ingredients.
Cosmetics: Used in formulations such as creams, lotions, shampoos, and other scented products.
Cleaning products: Its pleasant odor and solvent properties make it useful in household and industrial cleaning formulations.
Essential oils: Terpineol is a naturally occurring component of several essential oils and contributes to their characteristic aromas.
Chemical manufacturing: Used as an intermediate in the production of fragrances and other specialty chemicals.
Application
It’s mainly used in fragrance compositions, as a chemical intermediate, and as a precursor in the production of high purity alpha-terpineol.
Properties and Applications
α-Terpineol is a colorless, crystalline solid, smelling of lilac.
The most important commercial grade of terpineol consists of a liquid mixture of isomers that contains mainly α-terpineol and a considerable amount of γ-terpineol.
This mixture has a stronger lilac odor than does pure crystalline α-terpineol.
Hydrogenation of α-terpineol yields p-menthan-8-ol.
Terpineol is readily dehydrated by acids, yielding a mixture of unsaturated cyclic terpene hydrocarbons.
Under mildly acidic conditions, terpin hydrate is formed.
The most important reaction for the fragrance industry is esterification, particularly acetylation to terpinyl acetate.
Terpineol with its typical lilac odor is one of the most frequently used fragrance substances.
Terpineol is stable and inexpensive and is used in soaps and cosmetics.
Chemical Properties
α-Terpineol is a kind of clear colorless liquid after melting, which has a characteristic lilac odor with a sweet taste reminiscent of peach on dilution.
Chemical Information
Chemical name: Terpineol
Main isomer: α-Terpineol
Melting point: 31-35 °C (lit.)
Boiling point: 217-218 °C (lit.)
Density: 0.93 g/mL at 25 °C (lit.)
Vapor pressure: 6.48 Pa at 23℃
FLAVIS Number: 02.014 | alpha-Terpineol
Refractive index: 1.482-1.485
FEMA: 3045 | ALPHA-TERPINEOL
Flash point: 90 °C
Storage temp.: 2-8°C
Solubility: 0.71 g/L
pKa: 15.09±0.29 (Predicted)
Form: Liquid After Melting
Color: Clear colorless
Specific Gravity: 0.9386
Odor: at 100.00 %. pine terpene lilac citrus woody floral
Odor Type: terpenic
Water Solubility: negligible
Merck: 14,9171
JECFA Number: 366
BRN: 2325137
Henry's Law Constant: 4.4×100 mol/(m3Pa) at 25℃, Copolovici and Niinemets (2005)
Dielectric constant: 2.8（20℃）
Major Application: cleaning products, cosmetics, flavors and fragrances, food and beverages, personal care
InChI: 1S/C10H18O/c1-8-4-6-9(7-5-8)10(2,3)11/h4,9,11H,5-7H2,1-3H3
InChIKey: WUOACPNHFRMFPN-UHFFFAOYSA-N
Chemical class: Monoterpene alcohol
Appearance: Colorless to pale yellow liquid/solid
Odor: Floral, lilac-like, piney
Water solubility: Slightly soluble
Natural sources: Pine, tea tree, eucalyptus and other essential oils
“Terpineol” can refer to several structural isomers, including α-terpineol, β-terpineol, and γ-terpineol.
Therefore, physical properties can vary depending on the specific isomer or whether a commercial mixture is being described.
Occurrence
Reported found in more than 150 derivatives from leaves, herbs and flowers; the d-, l- and dl-isomers are known: the d-form is found in the essential oils from Cupressaceae in general; also in the oils of Elettaria cardamomum, star anise, marjoram, clary sage, neroli and others.
The l-form is found in Satureia montana, lavandin, cajeput, lime, lemon, cinnamon leaves and the distillates from Pinaceae (with exception of Pinus silvestris, which contains d-terpineol together with racemic form); likewise, Nectandra elaiophora (wood) and petitgrain bigarade.
The racemic form is found in cajenne linalool, Thymus caespititius, cajeput, Eucalyptus globulus; mixed with the l-form Terpineol is found in petitgrain; a nondefined form of terpineol has been reported in the bitter orange.
Reported found in over 260 natural sources including apple, apple juice, apricot, sweet and sour cherry, citrus peel oils and juices, orange, lemon, etc.
Uses
A naturally-occuring monoterpene alcohol.
Alpha-terpineol is used as an antioxidant, antiseptic, antihypernociception and anti-inflammatory.
Terpineol is also used as a solvent.
Terpineol is an important ingredient of pine oil disinfectants.
Further, Terpineol is used as a fragrance in perfumes, fat denaturant for soap production and synthetic flavoring agent.
Definition
ChEBI: A terpineol that is propan-2-ol substituted by a 4-methylcyclohex-3-en-1-yl group at position 2.
Preparation
Although α-terpineol occurs in many essential oils, only small quantities are isolated, for example, by fractional distillation of pine oils.
A common industrial method of α-terpineol synthesis consists of the hydration of α-pinene or turpentine oil with aqueous mineral acids to give crystalline cis-terpin hydrate (mp 117 °C), followed by partial dehydration to α-terpineol.
Suitable catalysts are weak acids or acid-activated silica gel.
Selective conversion of pinene, 3-carene, and limonene or dipentene to terpineol, without terpin hydrate formation is also used. Addition of organic acids (weak acids require catalytic amounts of mineral acids) produces terpinyl esters, which are subsequently hydrolyzed to terpineol, sometimes in situ.
Aroma threshold values
Detection: 280 to 350 ppb. Aroma characteristics in 1% ethanol: pine-like, woody and resinous with a slight cooling lemon and lime citrus nuance, and a floral dry out.
Taste threshold values
Taste characteristics at 2 to 25 ppm: woody, terpy, lemon and lemon–lime-like with a slight herbal and floral nuance.
Taste characteristics at 10 to 25 ppm: citrus woody with a lemon and lime nuance.
Terpineol has a slight soapy mouthfeel.
Flammability and Explosibility
Non flammable
Synthesis
Obtained from terpin hydrate by splitting off water; from pentane tricarboxylic acid by cyclization, followed by esterification to the hydroxy ester, then the unsaturated ester and Grignard to terpineol; also from isoprene and methyl vinyl ketone, using methyl magnesium iodide.
