<unk>  (para-dichlorobenzene or p-DCB) is a white solid with a strong, pungent odor, the characteristic smell of urinal cake.  It is an aromatic chemical compound having the chemical formula C6H4Cl2.  It consists of two chlorine atoms substituted onto a benzene ring.  It is used to control moths, molds, and mildew, and to deodorize restrooms and waste containers. Its primary use is in most modern mothballs in which it is a replacement for the more traditional naphthalene.  Trade names for p-DCB include Paramoth, Para crystals, and Paracide reflecting its widespread use as a pesticide to kill moths.  p-DCB is also used as a precursor in the production of the polymer poly(p-phenylene sulfide), and is used in urinal deodorant blocks because of its volatility.
When exposed to air, p-DCB slowly sublimates from a solid to a vapour. It is the vapour that acts as a deodorizer or insect killer. Most people recognize the odor as the smell of mothballs or urinal deodorant, and can smell p-DCB in the air at very low levels. Most p-DCB in the environment comes from its use in moth repellent products and in toilet deodorizer blocks.
1,4-Dichlorobenzene
Trichloroethylene
Methylene diphenyl diisocyanate
Coal tar
Tetrachloroethylene
Dimethylphthalate
2,4-Dinitrotoluene
Toluene diisocyanate