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I/GCSE Chemistry- Reactions with alkanes and alkenes

Triple and Double

August 22, 2021

This I/GCSE Chemistry blog post will look into the reactions involving alkanes and alkenes, let's get to it!

Combustion reactions

Alkanes: alkane + oxygen → carbon dioxide + water

Alkenes can also undergo combustion: alkene + oxygen → carbon dioxide + water

When alkenes combust, there is more soot (more carbon produced) due to higher carbon:hydrogen ratio in the molecules

Addition reactions

Alkenes are more reactive so can undergo addition reactions (when the double bond breaks and allows the carbon to form a bond with another atom)

E.g. Alkenes and bromine water (bromine water goes from orange to colourless as it reacts)

The product above is named 1,2-dibromoethane as the bromines are added to carbons numbers 1 and 2 and the result is a molecule with 2 bromines attached to an ethane molecule

Substitution reactions

Alkanes can also react with bromine water if exposed to UV light, so the bromine water goes from orange to colourless. 

The reaction bellow (if you pretend the chlorines are bromines) forms bromomethane and hydrogen bromide

That is all for this post!