Acenaphthene
Acenaphthene is a polycyclic aromatic hydrocarbon (PAH) consisting of naphthalene with an ethylene bridge connecting positions 1 and 8. It is a colourless solid. Coal tar consists of about 0.3% of this compound. Production and reactions
Acenaphthene was prepared the first time from coal tar by Marcellin Berthelot. Later Berthelot and Bardy synthesized the compound by cyclization of α-ethylnaphthalene. Industrially, it is still obtained from coal tar together with its derivative acenaphthylene (and many other compounds). Like other arenes, acenaphthene forms complexes with low valent metal centers. One example is (η6-acenaphthene)Mn(CO)3]+. Uses
It is used on a large scale to prepare naphthalene dicarboxylic anhydride, which is a precursor to dyes and optical brighteners. Naphthalene dicarboxylic anhydride is the precursor to perylenetetracarboxylic dianhydride, precursor to several commercial pigments and dyes. References

Polycyclic aromatic hydrocarbons
Tricyclic compounds