Mesitylene (also known as 1,3,5-trimethylbenzene, molecular formula C9H12) has a molecular structure in which the C atoms of the benzene ring form σ bonds with sp2 hybrid orbitals, and the other C atoms form σ bonds with sp3 hybrid orbitals. It is a functional group present in many organic compounds. It is an aromatic hydrocarbon obtained by symmetrically replacing three hydrogen atoms on the benzene ring with three methyl groups. It is widely present in coal tar and some petroleum. It is a colorless liquid, toxic, flammable and explosive. The freezing point is -44.72℃, the melting point is -44.7℃, the boiling point is 164.7℃, and the relative density is 0.8652 (20/4℃). Mesitylene can be oxidized with dilute nitric acid to produce 1,3,5-benzenetricarboxylic acid. Pure mesitylene is prepared by gas-phase catalytic dehydration of acetone at 300-500℃.