Reactions of Alkenes [H]

This lesson covers the reactions of alkenes as required by the AQA GCSE Chemistry specification (5.8.2). This is Higher Tier only [H] content. Alkenes are much more reactive than alkanes because of their C=C double bond, which can open up to allow other atoms to add across it. These addition reactions are the key reactions of alkenes.

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Why Are Alkenes Reactive?

Alkenes contain a C=C double bond, which makes them much more reactive than alkanes. The double bond is a region of high electron density that attracts other molecules and atoms.

The C=C double bond can break open, allowing atoms to add across the bond. This is why alkenes undergo addition reactions — the double bond breaks, and two new single bonds form.

Feature	Alkanes	Alkenes
Bonding	Single C–C bonds only	Contains C=C double bond
Saturation	Saturated	Unsaturated
Reactivity	Relatively unreactive	More reactive
Main reaction type	Combustion	Addition reactions