Xylenols are organic compounds with the formula (CH3)2C6H3OH. They are volatile colorless solids or oily liquids. They are derivatives of phenol with two methyl groups and a hydroxyl group. Six isomers exist, of which 2,6-xylenol with both methyl group in an ortho position with respect to the hydroxyl group is the most important. The name xylenol is a portmanteau of the words xylene and phenol.
2,4-dimethylphenol together with other xylenols and many other compounds are traditionally extracted from coal tar, the volatile materials obtained in the production of coke from coal. These residue contains a few percent by weight of xylenols as well as cresols and phenol. The main xylenols in such tar are the 3,5-, 2,4, and 2,3- isomers. 2,6-Xylenol is produced by methylation of phenol using methanol in the presence of metal oxide catalysts:
- C6H5OH + 2 CH3OH → (CH3)2C6H3OH + 2 H2O
The physical properties of the six isomeric xylenols are similar.
|Mp °C||43-45||63 - 65||22-23||70-73||62 - 68||61-64|
Together with cresols and cresylic acid, xylenols are an important class of phenolics with great industrial importance. They are used in the manufacture of antioxidants. Xylenol orange is a redox indicator built on a xylenol skeleton. 2,6-Xylenol is a monomer for poly(p-phenylene oxide) (PEO) engineering resins through carbon-oxygen oxidative coupling.
- Helmut Fiegein "Cresols and Xylenols" in Ullmann's Encyclopedia of Industrial Chemistry, 2007; Wiley-VCH, Weinheim. doi:10.1002/14356007.a08_025
- CRC Handbook of Tables for Organic Compound Identification, Third Edition, 1984, ISBN 0-8493-0303-6.