Cymene

For the ancient Greek city, see Cymene (Thessaly).

Cymene describes organic compounds with the formula CH₃C₆H₄CH(CH₃)₂. Three isomers exist: 1,2- 1,3-, and 1,4-. All are colorless liquids, immiscible in water, with similar boiling points. They are classified are aromatic hydrocarbons. The bearing two substituents: an isopropyl (CH(CH₃)₂) group and a methyl group.^[1]

Cymenes
Name	o-Cymene	m-Cymene	p-Cymene
Structural formula
CAS number	527-84-4	535-77-3	99-87-6
melting point (°C)	−71.54	−63.75	−67.94
boiling point (°C)	178.15	175.05	177.10

Production and reactions

m- and p-Cymene are prepared by alkylation of toluene with propylene:

CH₃C₆H₅ + 2 CH₃CH=CH₂ → CH₃C₆H₄CH(CH₃)₂

These alkylations are catalyzed by various Lewis acids, such as aluminium trichloride.

m- and p-Cymene are mainly of interest as precursors to the respective cresols, which exploits the Hock rearrangements.^[1]