Properties Use and Environmental Problems

Of the 12 known chlorobenzenes, six are of commercial importance (MCB, 1,2-DCB, 1,4-DCB, 1,2,4-TCB, 1,2,4,5-TeCB and HCB). Compounds with less chlorine are characterized by higher water solubility and higher vapor pressure or Henry coefficient (Table 9.3).

The toxicity of the chlorobenzenes also increases with increasing number of chlorine atoms. German production decreased steadily through the 1980s and 1990s as a result of stricter regulations. Emissions in the state of North-Rhine-Westphalia (Bayer Leverkusen, Germany) were estimated at 2886 t a-1 MCB and 1055 t a-1 DCB for 1992 (Dopper and Stock 1995). Three years earlier (1989), these emissions for the state of Hessen (Hoechst AG, Germany) were higher by a factor of nearly ten (Dopper and Stock 1995). These reductions result from the decrease in production and increase in efficiency of wastewater treatment.

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