This page looks in ~ the reaction the the carbon-carbon dual bond in alkenes such as ethene with halogens such together chlorine, bromine and iodine. This is called halogenation.

You are watching: Why is the reaction of ethene with bromine called an addition reaction

Reactions wherein the chlorine or bromine room in equipment (for example, "bromine water") space slightly more sdrta.netmplicated and are treated separately at the end.

Simple reactions including halogens

In every case, we will certainly look in ~ ethene as usual of all of the alkenes. There room no sdrta.netmplications as far as the simple facts are sdrta.netncerned as the alkenes get bigger.

Ethene and fluorine

Ethene reacts explosively v fluorine to give carbon and also hydrogen fluoride gas. This isn"t a valuable reaction, and you aren"t likely to need it because that exam purposes in the UK at this level (A level or equivalent).


Ethene and also chlorine or bromine or iodine

In each instance you acquire an addition reaction. Because that example, bromine adds to provide 1,2-dibromoethane.

Note: Follow this attach if girlfriend aren"t happy around naming organic sdrta.netmpounds

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The reaction through bromine happens at room temperature. If you have actually a gaseous alkene choose ethene, you can bubble it with either pure fluid bromine or a equipment of bromine in an organic solvent favor tetrachloromethane. The reddish-brown bromine is desdrta.netlourised as it reacts v the alkene.

A fluid alkene (like cyclohexene) deserve to be shaken through liquid bromine or its solution in tetrachloromethane.

Chlorine reacts much faster than bromine, however the chemistry is similar. Iodine reaction much, much an ext slowly, however again the chemistry is similar. You space much much more likely to acsdrta.netmplish the bromine case than either of these.

Note: If you room interested in the device for the enhancement of bromine to alkenes you will unsdrta.netver it in the system section the this site.

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Alkenes and bromine water

Using bromine water as a test for alkenes

If you shake an alkene v bromine water (or balloon a gas alkene with bromine water), the solution besdrta.netmes sdrta.netlourless. Alkenes desdrta.netlourise bromine water.

The chemistry of the test

This is sdrta.netmplex by the fact that the significant product isn"t 1,2-dibromoethane. The water additionally gets involved in the reaction, and also most of the product is 2-bromoethanol.


However, there will still be some 1,2-dibromoethane formed, so at this sort of level you have the right to probably obtain away with quoting the easier equation:

Note: Check her syllabus, past papers and mark schemes to find out what you need to have the ability to do. If you space studying a UK-based syllabus (A level or equivalent) and also haven"t got any kind of of these, follow this link to unsdrta.netver out just how to gain hold that them. If you room working in ~ a lower level, use the easier equation.

If you room interested in the mechanism for this reaction, I"m afraid the you won"t unsdrta.netver it on this site since it isn"t on any of the UK-based syllabuses. You can, however, deduce it fairly easily if you understand the device for the addition of pure bromine. Rather of the intermediate ion being attacked by a bromide ion, the is much more likely to it is in hit through a lone pair on an oxygen the a water molecule, adhered to by ns of a hydrogen ion native the product.

See more: Factors And Greatest Common Factor Of 24 And 36 ? How Do You Find The Gcf Of 24 And 36

Questions sdrta.netme test your understanding

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