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Hexachlorobenzene

Hexachlorobenzene (HCB) has been introduced commercially as a fungicide for wheat in 1933. It also had industrial uses in organic syntheses as a raw material for synthetic rubber and also had been used in production of fireworks and ammunition. The compound can be produced commercially by reacting benzene with excess chlorine in the presence of ferric chloride at 150-200 degrees Celsius.
Hexachlorobenzene is a chlorinated hydrocarbon industrial chemical but also it is formed as a waste product in the production of several chlorinated hydrocarbons such as tetrachloroethylene, trichloroethylene, and carbon tetrachloride, and is a contaminant in some pesticides such as pentachloronitrobenzene and pentachlorophenol. Hexachlorobenzene is also released in the environment due to ongoing use in developing countries and improper storage or disposal in developed countries. There are some indications that any process that produce dioxins or dibenzofurans (e.g., pulp and paper mills using chlorine for bleaching) will also yield other chlorinated organic compounds such as hexachlorobenzene. In addition, hexachlorobenzene may be produced as a byproduct in waste streams of chloralkali plants and wood preserving plants, and in fly ash and flue gas effluents from municipal incineration.
The United Nations Environment Program conducted a survey of import/export data for persistent organic pollutants worldwide which contain worldwide import/export data. From 1990-1994, 158.45 tons of hexachlorobenzene were exported worldwide, while 2258 tons of hexachlorobenzene were imported worldwide.
The technical grade used in agriculture contains 98 percent hexachlorobenzene, 1.8 percent pentachlorobenzene together with 0.2 percent 1,2,4,5tetrachlorobenzene. Commercial formulations (dusts) contain 10-ercent HCB alone or together with small quantities of lindane (0.51.0percent).

 


Structure formula of HCB


3D structure of HCB