Industrial uses of halogenated hydrocarbons

Few organic halides have direct use industri­ally. They are generally converted into other intermediate substances. For example, one of these substances is used to make vinyl chlo­ride, the building block for polyvinyl chloride. Polyvinyl chloride is noted for its hardness and resistance to chemicals. It is used in the pro­duction of floor coverings, pipes, and fabrics. Another important halogenated hydrocar-

Organic chemistry: Halogenated hydrocarbons 79

Ethene

Chloroethane molecules

1,2-dichloroethane

Chloroethane

Long-chain polymer molecule of polyvinyl chloride (PVC)

Polyvinyl chloride(PVC) is

a long-chain halogenated polymer. It can be made from ethene and chlorine in three main stages (illus­trated left. In the first stage, ethene is heated with chlo­rine to produce 1,2-di­chloroethane. In the second stage, the 1,2-dichloro-ethane is heated under pressure to produce chloro-ethene and hydrogen chlo­ride. After the hydrogen chloride has been removed, the pure chloroethene then remaining is heated in the presence of a catalyst to form PVC.

bon is methyl chloroform, which is used for degreasing, cleaning drains, and dissolving other substances. It is made via several syn­thetic steps from vinyl chloride.

Natural gas provides the principal source of compounds containing methane and a halo­gen. These include trichloromethane (chloro­form) and tetrachloromethane (carbon tetra­chloride). These two substances are used mainly as starting materials for the manufac­ture of fluorocarbon refrigerants called Fre-ons. Examples are trichlorofluoromethane (Freon-11) and dichlorodifluoromethane (Freon-12). These are widely used in refrigera­tors and air conditioners. Teflon (often used to coat the insides of cooking equipment) is also derived from a hydrocarbon containing meth­ane, carbon, and fluorine. A synthetic rubber called Neoprene is also produced from halogen-hydrocarbon compounds.

Date: 2015-12-11; view: 3828