Modern aromatics refer to a class of compounds that contain at least one benzene ring with a delocalized bond in the hydrocarbon molecule, and have unique properties (called aromaticity) different from open-chain compounds or alicyclic hydrocarbons. Such as benzene, naphthalene, anthracene, phenanthrene and its derivatives. Benzene is the simplest and most typical representative. They are prone to electrophilic substitution reactions, are relatively stable to heat, and are mainly derived from petroleum and coal tar.