3D model (JSmol)
|Molar mass||g·mol−1 136.238|
|Melting point||< −10 °C (14 °F; 263 K)|
|Boiling point||166 to 168 °C (331 to 334 °F; 439 to 441 K)|
Except where otherwise noted, data are 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 hydrocarbon. It is more precisely classified as a monoterpene. Monoterpenes are dimers of isoprenoid precursors, and myrcene is a significant component of the essential oil of several plants, including bay, cannabis, ylang-ylang, wild thyme, parsley, cardamom, 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 has not been found in nature, and is little used.
Terpenes arise naturally from dehydration of terpenol geraniol. Plants biosynthesize myrcene via geranyl pyrophosphate (GPP). The mevalonate pathway gives the precursors dimethylallyl pyrophosphate (Fig. 1a) and isopentenyl pyrophosphate (Fig.1b). These two precursors combine to produce GPP (Fig. 1c), which then isomerizes into linally pyrophosphate (Fig. 1d). The rearrangement and release of the pyrophosphate (OPP), and the double bond formation creates the product myrcene (Fig. 1e).
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. Many other plants contain myrcene, sometimes in substantial amounts. Some of these include cannabis, hops Houttuynia, lemon grass, mango, Myrcia, Verbena, West Indian bay tree, and cardamom.
Of the several terpenes extracted from Humulus lupulus (hops), the largest monoterpenes fraction is β-myrcene. One Swiss study of the chemical composition of the fragrance of Cannabis sativa L. found β-myrcene to compose between 29.4% to 65.8% of the steam-distilled essential oil for the set of fiber and drug strains tested.
Use in fragrance and flavor industries
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. Myrcene is converted to myrcenol, another fragrance found in lavender, via hydroamination of the 1,3-diene by diethylamine followed by hydrolysis and Pd-catalyzed removal of the amine.
- Merck Index, 11th Edition, 6243
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- Inui, T; Tsuchiya, F; Ishimaru, M; Oka, K; Komura, H (2013). “Different beers with different hops. Relevant compounds for their aroma characteristics”. Journal of Agricultural and Food Chemistry. 61 (20): 4758–64. doi:10.1021/jf3053737. PMID 23627300.
- Vázquez-Araújo, L; Rodríguez-Solana, R; Cortés-Diéguez, S. M.; Domínguez, J. M. (2013). “Use of hydrodistillation and headspace solid-phase microextraction to characterize the volatile composition of different hop cultivars”. Journal of the Science of Food and Agriculture. 93 (10): 2568–74. doi:10.1002/jsfa.6078. PMID 23483584.