Alkenes
Get to grips with alkenes — their structure, bonding, and shape. Learn what makes the C=C bond unique, why it locks molecules in place, and how to explain geometry with real examples.
Learn how molecules with the same atoms can look completely different. This section covers E/Z isomerism, the rules that define it, and how to name isomers using Cahn–Ingold–Prelog priority. Includes key diagrams and worked examples.
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Alkenes contain a double bond made of a sigma (σ) and a pi (π) bond — and it’s this weak π-bond that makes them much more reactive than alkanes. Because the π-electrons are more exposed, they break easily, letting alkenes undergo exciting addition reactions. From hydrogenation and halogenation to hydration and testing for unsaturation with bromine water, these reactions transform alkenes into useful compounds like alcohols and haloalkanes.
Alkenes react with electrophiles because of their electron-rich double bonds. This type of reaction is called electrophilic addition. You’ll see how molecules like HBr or Br₂ add across the double bond, forming new products through a short series of clear steps. We also cover why some products form more easily than others (hello, Markovnikov’s Rule) and how carbocation stability plays a role.
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This topic covers addition polymerisation of alkenes, including how polymers form, their properties, common examples like poly(ethene), and environmental issues such as disposal, recycling, and biodegradable alternatives