The trimethylbenzenes constitute a group of substances of aromatic hydrocarbons, which structure consists of a benzene ring with three methyl groups (âÂÂCH<sub>3</sub>) as a substituent. Through their different arrangement, they form three structural isomers with the molecular formula C<sub>9</sub>H<sub>12</sub>. They also belong to the group of C<sub>3</sub>-benzenes. The best-known isomer is mesitylene.