Ethene's Reaction with Bromine Water
* Unsaturated hydrocarbon: Ethene (C₂H₄) is an unsaturated hydrocarbon, meaning it has a carbon-carbon double bond.
* Electrophilic addition: The double bond in ethene is electron-rich and susceptible to attack by electrophiles (electron-loving species). Bromine (Br₂) is an electrophile.
* Color change: When bromine water (orange-brown solution) is added to ethene, the bromine adds across the double bond, forming 1,2-dibromoethane. This reaction consumes the bromine, causing the orange-brown color to disappear.
Polyethene's Structure
* Saturated hydrocarbon: Polyethene (also known as polyethylene) is a saturated hydrocarbon. It consists of long chains of carbon atoms linked by single bonds.
* No double bonds: Polyethene does not have any carbon-carbon double bonds.
Why Polyethene Doesn't React
Since polyethene lacks double bonds, it cannot undergo the electrophilic addition reaction with bromine that ethene does. Therefore, the bromine water will remain orange-brown, indicating no reaction.
In Summary
The key difference lies in the presence or absence of double bonds. Ethene's double bond makes it reactive with bromine water, while polyethene's lack of double bonds renders it unreactive.
