|Molar mass||136.23 g·mol−1|
|Melting point||< −10 °C (14 °F; 263 K)|
|Boiling point||166 to 168 °C (331 to 334 °F; 439 to 441 K)|
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
|what is: / ?)(|
Myrcene, or β-myrcene, is an olefinic natural organic compound. It is classified as a hydrocarbon, more precisely as a monoterpene. Terpenes are dimers of isoprene, and myrcene is one of the most important. It is a component of the essential oil of several plants including bay, cannabis, ylang-ylang, wild thyme, parsley, and hops. It is produced mainly semi-synthetically from myrcia, from which it gets its name. It is a key intermediate in the production of several fragrances. α-Myrcene is the name for the structural isomer 2-methyl-6-methylene-1,7-octadiene, which is not found in nature and is little used.
Biosynthesis and production
Terpenes arise naturally from dehydration of terpenol geraniol. It could in principle be extracted from any number of plants, for example wild thyme, the leaves of which contain up to 40% by weight of myrcene. The current route to commercial samples is by the pyrolysis (400 °C) of β-pinene, which is obtained from turpentine.
Use in fragrance industry
Myrcene is an important intermediate used in the perfumery industry. It has a pleasant odor, but is rarely used directly. It is also unstable in air, tending to polymerize. Samples are stabilized by the addition of alkylphenols or tocopherol. It is thus more highly valued as an intermediate for the preparation of flavor and fragrance chemicals such as menthol, citral, citronellol, citronellal, geraniol, nerol, and linalool. Treatment of myrcene with hydrogen chloride gives geranyl chloride, neryl chloride, and linalyl chloride. Treatment of these compounds with acetic acid gives geranyl acetate, neryl acetate, and linalyl acetate, respectively. These esters are then hydrolyzed to the corresponding alcohols. Myrcene is also converted to myrcenol, another fragrance found in lavender, via uncatalyzed hydroamination of the 1,3-diene followed by hydrolysis and Pd-catalyzed removal of the amine.
Myrcene has an analgesic effect and is likely to be responsible for the medicinal properties of lemon grass tea. It has antiinflammatory properties through Prostaglandin E2. The analgesic action can be blocked by naloxone or yohimbine in mice which suggests mediation by "alpha 2-adrenoceptor stimulated release of endogenous opioids".
Very high doses of myrcene potentiate barbiturate induced sleep in mice, further supporting the suggestions of sedative activity. It is likely that this is responsible for the use of hops and lemongrass as sedatives.
Partial list of the plants that contain myrcene
As mentioned above, many plants contain myrcene, sometimes in very large amounts.
- Merck Index, 11th Edition, 6243
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