1,4-Dichlorobenzene

p-DCB is produced by chlorination of benzene using ferric chloride as a catalyst: :C6H6 + 2 Cl2 → C6H4Cl2 + 2 HCl The chief impurity is the 1,2 isomer. The compound can be purified by fractional crystallization, taking advantage of its relatively high melting point of 53.5 °C; the isomeric dichlorobenzenes and chlorobenzene melt well below room temperature. == Uses ==

Disinfectant, deodorant, and pesticide disinfectant p-DCB is used to control moths, molds, and mildew. It also finds use as a disinfectant The chloride sites on p-DCB can be substituted with hydroxylamine and sulfide groups. In a growing application, p-DCB is the precursor to the high performance polymer poly(p-phenylene sulfide): : As ceruminolytic agent 2% Paradichlorobenzene used as a ceruminolytic agent for the treatment of impacted earwax. Recreational Use Recreational abuse of PDCB has been described, usually through use of urinal cakes. It is typically huffed. Deaths have been recorded from abuse. == Environmental and health effects ==

p-DCB is poorly soluble in water and is not easily broken down by soil organisms. Like many hydrocarbons, p-DCB is lipophilic and will accumulate in fatty tissues if consumed by a person or animal. The United States Department of Health and Human Services (DHHS) and the International Agency for Research on Cancer (IARC) have determined that p-DCB may reasonably be anticipated to be a carcinogen. This has been indicated by animal studies, although a full-scale human study has not been done. The United States Environmental Protection Agency (EPA) has set a target maximum contaminant level of 75 micrograms of p-DCB per liter of drinking water (75 μg/L), but publishes no information on the cancer risk. p-DCB is also an EPA-registered pesticide. The United States Occupational Safety and Health Administration (OSHA) has set a maximum level of 75 parts of p-DCB per million parts air in the workplace (75 ppm) for an 8-hour day, 40-hour workweek. A mechanism for the carcinogenic effects of mothballs and some types of air fresheners containing p-DCB has been identified in roundworms. Due to its carcinogenic nature, use of paradichlorobenzene in the European Union is forbidden as an air freshener (since 2005) and in mothballs (since 2008). Biodegradation Rhodococcus phenolicus is a bacterium species able to degrade dichlorobenzene as its sole carbon source. == See also ==