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| A B C D E F G H I J K L M N O P Q R S T U V W X Y Z |
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alkenes
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The presence of at least one double bond in alkenes means that they react in ways that alkanes cannot do. It allows, for example, alkenes to be distinguished from alkanes using a simple chemical test. This test involves the use of bromine water – a dilute solution of bromine which is normally orange-brown in color. Bromine water becomes colorless when shaken with an alkene, through an addition reaction, but is not decolorized by alkanes.
Alkene polymers and plastics
Under pressure and in the presence of a suitable catalyst, small alkenes will join together, by the opening up of their double bonds, to form long chains called polymers. The joining up of many individual alkene units by polymerization results in a variety of much-used and familiar plastics. These include polythene, polypropene, epoxy, polystyrene, and polychloroethene (PV).
Polythene, made from ethene, is very cheap and strong, and is easily molded. It is used to make, for example, plastic bags, bottles, and buckets. Polypropene, made from propene, has strong fibers and a high elasticity. It is used, for example, in the manufacture of crates, ropes, and carpets. Epoxy resins are polymers that can be used as adhesives. Polystyrene, made from styrene, is cheap, easily molded, and can be expanded into insulating forma. Polychloroethene (PVC) is made from chloroethene and used for making wire insulation and records.
Related category
• ORGANIC CHEMISTRY
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