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Reactions of Ethylene

 
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Oxidation

This is adding oxygen to the double bond - e.g., the oxidation of ethylene to ethylene oxide:


The oxidation of ethylene to form 1,2-ethanediol (ethylene glycol)

Ethylene oxide is used in the production of ethylene glycol (1,2-ethanediol), which has applications as an antifreeze and in the manufacture of polyesters by condensation polymerisation.

Halogenation

Reactions where a halogen (i.e. fluorine, chlorine, bromine, iodine, probably not astatine) are added to the double bond are called halogenation reactions. e.g., the conversion of ethylene to 1,2-dichoroethane


The chlorination of ethene to form 1,2-dichloroethane and the subsequent conversion of 1,2-dichloroethane to the monomer vinyl chloride.

1,2-Dichloroethane is a useful organic solvent used in dry-cleaing, and is also a valuable precursor in the synthesis of vinyl chloride (chloroethene), the monomer used in production of poly(vinyl chloride) (PVC).

Halogenation of the double-bond of ethylene can easily be done in the laboratory. 'Decolourisation' of bromine (Br2) was a common test for the presence of alkenes in the days before high resolution Nuclear Magnetic Resonance spectroscopy.

Vinyl chloride (chloroethene) is the monomer used to make poly(vinyl chloride), or PVC. Very many facts about this polymer can be found on the Macrogalleria web site (we considered nicking huge slabs of their site, but thought better of it).

Alkylation

Adding a hydrocarbon to the double bond, e.g. the synthesis of ethylbenzene from ethylene and benzene:


The conversion of benzene and ethylene into ethylbenzene followed by the conversion to styrene.

Ethylbenzene is an intermediate for the production of styrene, one of the most widely used vinyl monomers.

Styrene is the monomer used to make polystyrene, familiar to you from such specialty applications as polystyrene cups and eskys.

Hydration

The reaction that adds water to the double bond is called hydration. The most important industrial application of this reaction is the conversion of ethylene to ethanol.

Most industrial ethanol is made this way, and not by the fermentation of sugars (see section 9.2.2 of our Discovery website, sugar fermentation is only used to make ethanol for human consumption, not that polymer chemists ever do that sort of thing...). This is an indication of how the fact that the quantity of fossil fuels available is finite has not yet been translated into economic reality.


The hydration of ethene to form industrial grade ethanol

Jargon Busters...

In the reactions above, MPa stands for "megapascal", that is, one million pascal. A pascal is the pressure generated by a mass of approximately 100g on a square metre under the earth's gravitational field. Atmospheric pressure is about 100,000 pascal (100 kPa, or as weather forecasters like to say, 1000 hPa [hectopascal]), so 7 MPa is about 70 times atmospheric pressure.

Non-metric units are still in use in three countries, including Brunei and Myanmar. You may come across values in "psi", or "pound force per square inch": 1 MPa is about 145 psi.