P-Cymene Explained

p-Cymene is a naturally occurring aromatic organic compound. It is classified as an alkylbenzene related to monocyclic monoterpenes.[1] 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.

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 propene.[2]

Related compounds

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 [(''η''<sup>6</sup>-cymene)RuCl<sub>2</sub>]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.

References

  1. Balahbib . Abdelaali . El Omari . Nasreddine . Hachlafi . Naoufal EL. . Lakhdar . Fatima . El Menyiy . Naoual . Salhi . Najoua . Mrabti . Hanae Naceiri . Bakrim . Saad . Zengin . Gokhan . Bouyahya . Abdelhakim . 2021-07-01 . Health beneficial and pharmacological properties of p-cymene . Food and Chemical Toxicology . 153 . 112259 . 10.1016/j.fct.2021.112259 . 0278-6915.
  2. Encyclopedia: Alkylation. Bipin V.. Vora. Joseph A.. Kocal. Paul T.. Barger. Robert J.. Schmidt. James A.. Johnson. 2003. Kirk‐Othmer Encyclopedia of Chemical Technology. 10.1002/0471238961.0112112508011313.a01.pub2. 0471238961.
  3. M. A. . Bennett . T.-N. . Huang . T. W. . Matheson . A. K. . Smith . (η6-Hexamethylbenzene)Ruthenium Complexes . . 1982 . 21 . 74–78 . 10.1002/9780470132524.ch16. 9780470132524 .