Mésitylène

Mesitylene or 1,3,5-trimethylbenzene is a derivative of benzene with three methyl substituents positioned symmetrically around the ring. The other two isomeric trimethylbenzenes are 1,2,4-trimethylbenzene (pseudocumene) and 1,2,3-trimethylbenzene (hemimellitene). All three compounds have the formula C6H3(CH3)3, which is commonly abbreviated C6H3Me3. Mesitylene is a colorless liquid with sweet aromatic odor. It is a component of coal tar, which is its traditional source. It is a precursor to diverse fine chemicals. The mesityl group (Mes) is a substituent with the formula C6H2Me3 and is found in various other compounds. Mesitylene is prepared by transalkylation of xylene over solid acid catalyst: 2 C6H4(CH3)2 ⇌ C6H3(CH3)3 + C6H5CH3 C6H4(CH3)2 + CH3OH → C6H3(CH3)3 + H2O Although impractical, it could be prepared by trimerization of propyne, also requiring an acid catalyst, yields a mixture of 1,3,5- and 1,2,4-trimethylbenzenes. Trimerization of acetone via aldol condensation, which is catalyzed and dehydrated by sulfuric acid is another method of synthesizing mesitylene. Oxidation of mesitylene with nitric acid yields trimesic acid, C6H3(COOH)3. Using manganese dioxide, a milder oxidising agent, 3,5-dimethylbenzaldehyde is formed. Mesitylene is oxidised by trifluoroperacetic acid to produce mesitol (2,4,6-trimethylphenol). Bromination occurs readily, giving mesityl bromide: (CH3)3C6H3 + Br2 → (CH3)3C6H2Br + HBr Mesitylene is a ligand in organometallic chemistry, one example being the organomolybdenum complex [(η6-C6H3Me3)Mo(CO)3] which can be prepared from molybdenum hexacarbonyl. Mesitylene is mainly used as a precursor to 2,4,6-trimethylaniline, a precursor to colorants. This derivative is prepared by selective mononitration of mesitylene, avoiding oxidation of the methyl groups. ] Mesitylene is used in the laboratory as a specialty solvent. In the electronics industry, mesitylene has been used as a developer for photopatternable silicones due to its solvent properties.