Dechlorination aromatic hydrocarbons

Reductive dehalogenation of chlorinated phenols to phenol, cyclohexanol and other chlorine-free compounds takes place rapidly with hydrogen gas and Pd/C in an aqueous system or under solvent-free conditions. Thus, pentachloro phenol was able to be completely dechlorinated within 20 min (Scheme 4.45). This methodology enables a facile route for rapid and complete detoxification of highly toxic polychlorinated aromatic hydrocarbons and environmental remediation71,72. 

Rates of anaerobic dechlorination of aromatic hydrocarbons (Peijnenburg et al. 1992) and of the hydrolysis of aromatic nitriles under anaerobic conditions (Peijnenburg et al. 1993) have been correlated with a number of parameters including Hammett o-constants, inductive parameters, and evaluations of the soil/ water partitioning. 

Reductive DechIorina.tion. Such reduction of chlorinated aUphatic hydrocarbons, eg, lindane, has been known since the 1960s. More recentiy, the dechlorination of aromatic pesticides, eg, 2,4,5-T, or pesticide products, eg, chlorophenols, has also been documented (eq. 10) (20). These reactions are of particular interest because chlorinated compounds are generally persistent under aerobic conditions. 

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