p-Cymene

p-Cymene is a naturally occurring aromatic organic compound. It is classified as an alkylbenzene related to a monoterpene. Its structure consists of a benzene ring para-substituted with a methyl group and an isopropyl group. p-Cymene is insoluble in water, but miscible with organic solvents.

"Cymene" redirects here. For the other isomers, see Cymenes. For the ancient city of Thessaly, see Cymene (Thessaly).
p-Cymene
Skeletal formula
Ball-and-stick model
Names
Preferred IUPAC name
1-Methyl-4-(propan-2-yl)benzene[1]
Other names
para-Cymene
4-Isopropyltoluene
4-Methylcumene
Paracymene
Identifiers
3D model (JSmol)
3DMet
1903377
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.002.542
EC Number
  • 202-796-7
305912
KEGG
RTECS number
  • GZ5950000
UNII
UN number 2046
Properties
C10H14
Molar mass 134.222 g·mol−1
Appearance Colourless liquid
Density 0.857 g/cm3
Melting point −68 °C (−90 °F; 205 K)
Boiling point 177 °C (351 °F; 450 K)
23.4 mg/L
−1.028×10−4 cm3/mol
Hazards
GHS pictograms
GHS Signal word Danger
GHS hazard statements
 H226, H304, H411
P210, P233, P240, P241, P242, P243, P273, P280, P301+310, P303+361+353, P331, P370+378, P391, P403+235, P405, P501
Flash point 47 °C (117 °F; 320 K)
435 °C (815 °F; 708 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Isomers and production

In addition to p-cymene, two less common geometric isomers are o-cymene, in which the alkyl groups are ortho-substituted, and m-cymene, in which they are meta-substituted. p-Cymene is the only natural isomer, as expected from the terpene rule. All three isomers form the group of cymenes.

Cymene is also produced by alkylation of toluene with propylene.[2]

It is a constituent of a number of essential oils, most commonly the oil of cumin and thyme. Significant amounts are formed in sulfite pulping process from the wood terpenes.

p-Cymene is a common ligand for ruthenium. The parent compound is [(η6-cymene)RuCl2]2. This half-sandwich compound is prepared by the reaction of ruthenium trichloride with the terpene α-phellandrene. The osmium complex is also known.[3]

Hydrogenation gives the saturated derivative p-menthane.

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References
  1. Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. pp. 139, 597. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4.
  2. Vora, Bipin V.; Kocal, Joseph A.; Barger, Paul T.; Schmidt, Robert J.; Johnson, James A. (2003). "Alkylation". Kirk-Othmer Encyclopedia of Chemical Technology. Kirk‐Othmer Encyclopedia of Chemical Technology. doi:10.1002/0471238961.0112112508011313.a01.pub2. ISBN 0471238961.
  3. Bennett, M. A.; Huang, T.-N.; Matheson, T. W.; Smith, A. K. (1982). "(η6-Hexamethylbenzene)Ruthenium Complexes". Inorganic Syntheses. 21: 74–78. doi:10.1002/9780470132524.ch16.
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