Vinyl chloride The largest application of<unk>  chemistry is the production of vinyl chloride. The annual production in 1985 was around 13 million tons, almost all of which was converted into polyvinylchloride (PVC). Chloromethanes Most low molecular weight chlorinated hydrocarbons such as chloroform, dichloromethane, dichloroethene, and trichloroethane are useful solvents. These solvents tend to be relatively non-polar; they are therefore immiscible with water and effective in cleaning applications such as degreasing and dry cleaning. Several billion kilograms of chlorinated methanes are produced annually, mainly by chlorination of methane: :CH4 + x Cl2 → CH4−xClx + x HCl The most important is dichloromethane, which is mainly used as a solvent. Chloromethane is a precursor to chlorosilanes and silicones. Historically significant, but smaller in scale is chloroform, mainly a precursor to chlorodifluoromethane (CHClF2) and tetrafluoroethene which is used in the manufacture of Teflon. Pesticides The two main groups of<unk>  insecticides are the DDT-type compounds and the chlorinated alicyclics. Their mechanism of action differs slightly. *The DDT like compounds work on the peripheral nervous system. At the axon's sodium channel, they prevent gate closure after activation and membrane depolarization. Sodium ions leak through the nerve membrane and create a destabilizing negative "afterpotential" with hyperexcitability of the nerve. This leakage causes repeated discharges in the neuron either spontaneously or after a single stimulus. *Chlorinated cyclodienes include aldrin, dieldrin, endrin, heptachlor, chlordane and endosulfan. A 2- to 8-hour exposure leads to depressed central nervous system (CNS) activity, followed by hyperexcitability, tremors, and then seizures. The mechanism of action is the insecticide binding at the GABAA site in the gamma-aminobutyric acid (GABA) chloride ionophore complex, which inhibits chloride flow into the nerve. *Other examples include dicofol, mirex, kepone, and pentachlorophenol. These can be either hydrophilic or hydrophobic, depending on their molecular structure. Insulators Polychlorinated biphenyls (PCBs) were once commonly used electrical insulators and heat transfer agents. Their use has generally been phased out due to health concerns. PCBs were replaced by polybrominated diphenyl ethers (PBDEs), which bring similar toxicity and bioaccumulation concerns.
Organochlorine compound
Persistent organic pollutant
Organobromine compound
Corrosive substance
Polycyclic aromatic hydrocarbon
Perfluorinated compound
Dioxins and dioxin-like compounds
Polychlorinated dibenzodioxins