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Saturday, December 20, 2008

Haloalkane,alkyl halogenide, halogenalkane or halogenoalkane, and alkyl halide,fluoroalkanes, chloroalkanes, bromoalkanes and iodoalkanes,Polymer

The haloalkanes (also known as halogenoalkanes or alkyl halides) are a group of chemical compounds, consisting of alkanes, such as methane or ethane, with one or more halogens linked, such as chlorine or fluorine, making them a type of organic halide. They are known under many chemical and commercial names. As flame retardants, fire extinguishants, refrigerants, propellants and solvents they have or had wide use. Some haloalkanes (those containing chlorine or bromine) have been shown to have negative effects on the environment such as ozone depletion. The most widely known family within this group are the chlorofluorocarbons (CFCs).


A haloalkane also known as alkyl halogenide, halogenalkane or halogenoalkane, and alkyl halide is a chemical compound derived from an alkane by substituting one or more hydrogen atoms with halogen atoms. Substitution with fluorine, chlorine, bromine, and iodine results in fluoroalkanes, chloroalkanes, bromoalkanes and iodoalkanes, respectively. Mixed compounds are also possible, the best-known examples being the chlorofluorocarbons (CFCs) which are mainly responsible for ozone depletion. Haloalkanes are used in semiconductor device fabrication, as refrigerants, foam blowing agents, solvents, aerosol spray propellants, fire extinguishing agents, and chemical reagents.

Freon is a trade name for a group of chlorofluorocarbons used primarily as a refrigerant. The word Freon is a registered trademark belonging to DuPont.

There are 3 types of haloalkanes. In primary (1°) haloalkanes the carbon which carries the halogen atom is only attached to one other alkyl group. However CH3Br is also a primary haloalkane, even though there is no alkyl group. In secondary (2°) haloalkanes the carbon that carries the halogen atom is attached to 2 alkyl groups. In tertiary (3°) haloalkanes the carbon that carries the halogen atom is attached to 3 alkyl groups.

Hydro fluoro compounds (HFC)

Hydrofluorocarbons (HFCs) contain no chlorine. They are composed entirely of carbon, hydrogen, and fluorine. They have no known effects at all on the ozone layer. Only compounds containing chlorine and bromine are thought to harm the ozone layer. Fluorine itself is not ozone-toxic. However, HFCs and perfluorocarbons do have activity in the entirely different realm of greenhouse gases, which do not destroy ozone, but do cause global warming. Two groups of haloalkanes, hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs), are targets of the Kyoto Protocol. Allan Thornton, President of Environmental Investigation Agency, an environmental watchdog, says that HFCs are up to 12,500 times as potent as carbon dioxide in global warming. Wealthy countries are clamping down on these gases. Thornton says that many countries are needlessly producing these chemicals just to get the carbon credits. Thus, as a result of carbon trading rules under the Kyoto Protocol, nearly half the credits from developing countries are from HFCs, with China scoring billions of dollars from catching and destroying HFCs that would be in the atmosphere as industrial byproducts.

Polymer haloalkanes

Chlorinated or fluorinated alkenes can be used for polymerization, resulting in polymer haloalkanes with notable chemical resistance properties. Important examples include polychloroethene (polyvinyl chloride, PVC), and polytetrafluoroethene (PTFE, or Teflon), but many more halogenated polymers exist.

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