Formula C10H18O Molar mass 154.25 g/mol Melting point 18 °C Appearance Colorless liquid | Boiling point 219 °C Density 934 kg/m³ | |
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Terpineol is a naturally occurring monoterpene alcohol that has been isolated from a variety of sources such as cajuput oil, pine oil, and petitgrain oil. There are four isomers, alpha-, beta-, gamma-terpineol, and terpinen-4-ol. beta- and gamma-terpineol differ only by the location of the double bond. Terpineol is usually a mixture of these isomers with alpha-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 constituents of lapsang souchong tea; the α-terpineol originates in the pine smoke used to dry the tea. (+)-α-Terpineol is a chemical constituent of skullcap.
Synthesis
Although it is naturally occurring, terpineol is commonly manufactured from the more readily available alpha-pinene.
In one study, an alternative route starting from d-limonene was demonstrated:
Limonene is reacted with trifluoroacetic acid in a Markovnikov addition to a trifluoroacetate intermediate, which is easily hydrolyzed with sodium hydroxide to α-terpineol with 76% selectivity. Side-products are the β-terpineol in a mixture of the cis-isomer, the trans-isomer, and 4-terpineol.
