Nahalene is an organic compound with formula CââHâ. It is the simplest polycyclic aromatic hydrocarbon, and is a white crystald with a characteristic odor that is detectable at concentrations as low as 0.08 ppm by mass. As an aromatic hydrocarbon, nahalene's structure consists of a fused pair of benzene rings. It is best known as the main ingredient of traditional mothballs.