All About Alkenes

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Uses of alkenes

Alkenes are produced from the alkanes in crude oil by a process called cracking. Cracking uses heat and a catalyst to decompose alkanes. The cracking process is important because it turns less useful alkanes into more useful smaller ones and produces very useful alkenes like ethene, the starting material for many plastics.

catalyst: A substance which speeds up a chemical reaction without being altered or consumed in the process itself.

Alkenes are unsaturated hydrocarbons with one double bond (R-C=C-R). They are from a homologous series with the general formula CnH2n. The 1st member to possess this functional group is ethane, C2H4. Ethene is an important raw material for the petrochemical industry. In fact, more commercial chemicals are produced from Ethene than from any other hydrocarbon intermediate. This unique position of ethene is due to favorable inherent properties as summarized below :

i. Simple but reactive structure
ii. Inexpensive
iii. Easily available through cracking of hydrocarbons

Alkenes are much more reactive than alkanes because alkenes are unsaturated (they have a reactive double bond). An alkene may be distinguished from an alkane by shaking the hydrocarbon with bromine water. Bromine water is reddish-brown, and will decolourised with an alkene but not with an alkane. Bromine adds across the double bond of an alkene to form a colourless dibromo alkane. This is an example of an addition reaction. An addition reaction occurs when two or more reactants join together to form a single product.

Uses of alkenes

Alkenes are extremely important in the manufacture of plastics. All plastics are in some way related to alkenes. The names of some plastics (Polythene or Poly Ethene, Polypropene), relate to their alkene partners. Plastics are used for all kinds of tasks, from packaging and wrapping, to clothing and outdoor apparel.

Lower alkenes are used as fuel and illuminant. These may be obtained by the cracking of kerosene or petrol.

For the manufacture of a wide variety of polymers, e.g., polyethene, polyvinylchloride (PVC) and teflon etc.

As raw materials for the manufacture of industrial Chemicals such as alcohols, aldehydes, and etc.

Besides, alkenes also used for artificial ripening of fruits, as a general anesthetic, for making poisonous mustard gas (War gas) and ethylene-oxygen flame.

References :

1. GCSE Science

2. Chemistry Guide

3. Carbon Chemistry

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January 31, 2010 - Posted by | Uncategorized

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