Xylenol

The Xylenols or dimethylphenols form a group of aromatic compounds with two methyl groups and one hydroxyl group in chemistry. They can be regarded as hydroxy derivatives of xylenes or dimethyl derivatives of phenol. There are thus six isomers. The name xylenol derived from the combination of the names of the aromatics xylene and phenol.

Structure and Properties

The physical properties of the six xylenol isomers similar. The Xylenols in water are usually only very slightly soluble. They are colorless to yellowish needles or plates with a pungent odor. Chemically, they behave like typical phenols, they form, for example, in alkaline solution phenolates, which have a much higher water solubility.

The methyl groups exert a (weak) I effect of the aromatics, which the electron density is increased in the ring. This inter alia, the acidity of the phenolic OH is weakened. The pKa value will be somewhat higher than that of the phenol (9.99 ) and the cresols.

Occurrence

All Xylenols are found in coal tar and beech wood and are a component of the mixture creosote.

Representation

Xylenols can be represented as a rule of the xylidines by diazotization and subsequent boiling of the diazonium salt.

Use

Together with the cresols and cresol are Xylenols an important class of phenols with great industrial importance. Xylenols be used as starting materials for the synthesis of pesticides, antioxidants, and pharmaceuticals ( eg, mexiletine ). 2,5-xylenol (p- xylenol ) serves as the basis for the representation of the pH indicators Xylenolphthalein, xylenol and bromoxylenol blue. From 2,6- xylenol is metalphthalein and xylenol orange derive, they are used as indicators in complexometric. 2,6-xylenol is used as a starting material for the synthesis of polyphenylene ether. By chlorination of 3,5-xylenol, the disinfectant chloroxylenol is accessible.