Myrcene

Myrcene[1]
IUPAC name 7-Methyl-3-methylene-1,6-octadiene
Identifiers
CAS number	123-35-3 Y
PubChem	31253
ChemSpider	28993 Y
KEGG	C06074 Y
ChEBI	CHEBI:17221 N
ChEMBL	CHEMBL455491 Y
Jmol-3D images	Image 1
SMILES CC(=CCCC(=C)C=C)C
InChI InChI=1S/C10H16/c1-5-10(4)8-6-7-9(2)3/h5,7H,1,4,6,8H2,2-3H3 Y Key: UAHWPYUMFXYFJY-UHFFFAOYSA-N Y InChI=1/C10H16/c1-5-10(4)8-6-7-9(2)3/h5,7H,1,4,6,8H2,2-3H3 Key: UAHWPYUMFXYFJY-UHFFFAOYAT
Properties
Molecular formula	C10H16
Molar mass	136.23 g mol−1
Density	0.794 g/cm3
Melting point	< -10 °C
Boiling point	166-168 °C[2]
N (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

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, ylang-ylang, wild thyme, and hops.^[3][4] 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.^[5]

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 pinene, which is obtained from turpentine.^[5]

Use in fragrance industry

Myrcene is an important intermediate used in the perfumery industry. It has 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 acetate 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.

As 1,3-dienes, both myrcene and mycenol undergo Diels-Alder reactions with several dienophiles such as acrolein to give cyclohexene derivatives that are also useful fragrances.^[2]

Compendial status

• British Pharmacopoeia^[6]

Partial list of the plants that contain myrcene

As mentioned above, many plants contain myrcene, sometimes in very large amounts.^[5]

• Houttuynia
• Mangoes
• Cannabis spp.
• Hops
• Lemon grass
• West Indian Bay Tree
• Verbena
• Mercia

See also

• Perfume allergy

References

1. ^ Merck Index, 11th Edition, 6243
2. ^ ^{a b} Karl-Georg Fahlbusch, Franz-Josef Hammerschmidt, Johannes Panten, Wilhelm Pickenhagen, Dietmar Schatkowski, Kurt Bauer, Dorothea Garbe, Horst Surburg “Flavors and Fragrances” in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. doi:10.1002/14356007.a11_141
3. ^ Chyau, Charng-Cherng et al.; Mau, Jeng-Leun; Wu, Chung-May (1996). "Characteristics of the Steam-Distilled Oil and Carbon Dioxide Extract of Zanthoxylum simulans Fruits". Journal of Agricultural and Food Chemistry 44 (4): 1096–1099. doi:10.1021/jf950577d. 
4. ^ Glenn Tinseth, "Hop Aroma and Flavor", January/February 1993, Brewing Techniques. <http://realbeer.com/hops/aroma.html> Accessed July 21, 2010.
5. ^ ^{a b c} Arno, B. and Leif, J., "Myrcene as a Natural Base Chemical in Sustainable Chemistry: A Critical Review", ChemSusChem, 2009, volume 2, pp. 1072-1095. doi:10.1002/cssc.200900186
6. ^ The British Pharmacopoeia Secretariat (2009). "Index, BP 2009". http://www.pharmacopoeia.co.uk/pdf/2009_index.pdf. Retrieved 31 March 2010.