alpha-Terpineol

Description

α-Terpineol is a terpene alcohol that is found in natural oils such as pine oil and petitgrain (the oil from the bitter orange tree). It is the most common of four structural isomers; the others are β-, γ-, and 4-terpineol. It should not be confused with terpinol, the hydrate of terpin, a terpene diol.
α-Terpineol is a racemic mixture of (R)-(+)- and (S)-(–)-enantiomers. Both are found in nature; but the article of commerce, which is usually synthesized from α-pinene, is the racemate. In 1903, German chemists H. Waldbaum and O. Hüthig isolated the (+)-stereoisomer from petitgrain. Four years later, J. E. Teeple of New York City separated its enantiomer from?long-leaf pine oil.
The lilac-like aroma of α-terpineol makes it a desirable ingredient for perfumes and cosmetics. This time of year, people burn α-terpineol-scented candles for their piney scent. Whatever your favorite aroma during the holidays, enjoy the season!

Chemical properties

Clear colorless liquid after melting

Chemical properties

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. It is stable and inexpensive and is used in soaps and cosmetics.

Chemical properties

α-Terpineol has a characteristic lilac odor with a sweet taste reminiscent of peach on dilution.

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 it 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, lime, grapefruit, tangerine, mandarin peels oils and juices, bergamot, cranberry, blueberry, black currant, raspberry, strawberry, guava, grapes, raisin, melon, papaya, peach, pear, pineapple, carrot, celery, peas, potato, bell pepper, tomato, anise, cinnamon, clove, cumin seed, ginger, Mentha oils, pepper, mace, parsley, nutmeg, thyme, Gruyere cheese, parmesan cheese, butter, cooked chicken and beef, hop oil, beer, cognac, rum, wines, tea, nuts, honey, avocado, passion fruit, prune, plums, beans, mushroom, sweet and wild marjoram, starfruit, mango, tamarind, parsnip root, cardamom, coriander seed, rice, quince, litchi, calamus, dill, licorice, lovage root, juniper berry, corn oil, laurel, sweet and bitter fennel, wort, elderberry, loquat, myrtle berry, rosemary, buchu oil, Bourbon vanilla, mountain papaya, turmeric, clary sage, lemon balm, nectarines, naranjilla fruit, cape gooseberry and sea buckthorn.

The Uses of alpha-Terpineol

A naturally-occuring monoterpene alcohol.Alpha-terpineol is used as an antioxidant, antiseptic, antihypernociception and anti-inflammatory. It is also used as a solvent. It is an important ingredient of pine oil disinfectants. Further, it is used as a fragrance in perfumes, fat denaturant for soap production and synthetic flavoring agent.

The Uses of alpha-Terpineol

Shows antioxidant effects. Antiseptic. is present in many extracted oils of various plant species, acts as an antihypernociception and anti-inflammatory.

What are the applications of Application

α-Terpineol is a monoterpene alcohol and a terpenoid building block for proteomic research and is a

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. It has a slight soapy mouthfeel.

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.

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.