<unk>  is an organic compound with formula . It is the simplest polycyclic aromatic hydrocarbon, and is a white crystalline solid with a characteristic odor that is detectable at concentrations as low as 0.08 ppm by mass. As an aromatic hydrocarbon,<unk> 's structure consists of a fused pair of benzene rings. It is best known as the main ingredient of traditional mothballs.
Naphthalene
Nitrobenzene
Benzene
Vinyl chloride
Alkylphenol
Polychlorinated naphthalene
Coal tar
Vinyl halide